Version July 2025
INTRODUCTION —
Urticaria, or hives (sometimes referred to as welts or wheals), is a common disorder, with a lifetime prevalence of approximately 20 percent in the general population [1]. A typical urticarial lesion is an intensely pruritic, erythematous plaque (picture 8C). Urticaria is sometimes accompanied by angioedema, which is swelling deeper in the skin. A presumptive trigger, such as a drug, food ingestion, insect sting, or infection, may be identifiable in patients with new-onset urticaria, although no specific cause is found in many cases, particularly when the condition persists for weeks or months. (See 'Etiologies and pathophysiology' below.)
The epidemiology, clinical manifestations, etiologies, diagnosis, evaluation, and management of new-onset urticaria will be reviewed here. Chronic urticaria and isolated angioedema are discussed separately:
●(See "Chronic spontaneous urticaria: Standard management and patient education".)
●(See "An overview of angioedema: Clinical features, diagnosis, and management".)
ACUTE VERSUS CHRONIC —
Urticaria (with or without angioedema) is commonly categorized by its chronicity:
●Acute urticaria – Urticaria is considered acute when it has been present for less than six weeks. More than two-thirds of cases of new-onset urticaria will resolve within this timeframe, and often resolution is within one to three weeks [2].
●Chronic urticaria – Urticaria is considered chronic when it is recurrent, with signs and symptoms occurring most days of the week, for six weeks or longer.
In this topic review, we use the term "new-onset" urticaria to refer to symptoms that began within the previous six weeks and have not yet resolved. The lesions of acute and chronic urticaria are identical in appearance, so when the problem first develops, it is not possible to differentiate the two disorders. The period of six weeks is somewhat arbitrary and simply represents a timeframe in which new cases of urticaria usually resolve [3].
EPIDEMIOLOGY —
Urticaria affects up to 20 percent of people at some point in their lives and occurs across the age spectrum [4]. The prevalence is somewhat higher in children between one and four years of age compared with other age groups and in females compared with males [5].
CLINICAL MANIFESTATIONS —
Patients with new-onset urticaria may present with urticaria, urticaria with angioedema, or isolated angioedema. Angioedema is a manifestation of the same pathophysiologic process in the deeper layers of the skin and subcutaneous tissues. One-third of patients present with both urticaria and angioedema, 30 to 40 percent with isolated urticaria, and 10 to 20 percent with angioedema alone [6].
Urticarial lesions are circumscribed, raised, erythematous plaques, often with central pallor (picture 1). Lesions may be round, oval, or serpiginous in shape and vary in size from less than 1 centimeter to several centimeters in diameter. They are intensely itchy. Pruritus may disrupt work, school, or sleep. Symptoms often seem most severe at night.
Individual lesions are transient, usually appearing and enlarging over the course of minutes to hours and then disappearing within 24 hours. Lesions may coalesce as they enlarge (picture 2A-B). Urticarial lesions are not normally painful and resolve without leaving residual ecchymotic marks on the skin, unless there is trauma from scratching. If lesions are long lasting, painful, or leave residual bruising, the diagnosis of urticarial vasculitis should be considered. (See 'Conditions to exclude' below.)
Any area of the body may be affected, although areas in which clothing compresses the skin (eg, under waistbands) or skin rubs together (axillae) are sometimes affected more dramatically. The areas of the body affected generally provide no information about likely etiology unless there is a history of specific contact (eg, urticaria limited to the hands and arms in a patient employed in seafood processing).
Angioedema is nondependent swelling of the skin with poorly defined borders and varying degrees of erythema (picture 3). Angioedema commonly affects the face and lips, extremities, and/or genitals. However, patients who present with angioedema without urticaria should also be evaluated for other angioedema disorders, such as drug-induced angioedema (eg, angiotensin-converting enzyme [ACE] inhibitors), and hereditary and acquired C1 inhibitor deficiency. (See "ACE inhibitor-induced angioedema" and "An overview of angioedema: Pathogenesis and causes".)
ETIOLOGIES AND PATHOPHYSIOLOGY —
Urticaria is mediated by cutaneous mast cells and basophils in the superficial dermis, and angioedema is mediated by these cells deeper in the skin and subcutaneous tissues. Mast cells and basophils release multiple mediators upon activation, including histamine (which causes itching) and vasodilatory mediators (which cause localized swelling in the uppermost layers of the skin). The same process gives rise to angioedema when mast cells deeper in the dermis and subcutaneous tissues are activated. Mast cells and basophils can be activated through various mechanisms; mast cells have receptors for immunoglobulin E (IgE), as well as receptors that recognize certain chemical motifs on drugs, complement fragments, neuropeptides, microbial proteins, and other substances. (See "Mast cells: Development, identification, and physiologic roles" and "Mast cells: Surface receptors and signal transduction", section on 'Activating receptors'.)
The common etiologies of urticaria are described below and summarized in the table (table 1). Patients with acute urticaria are more likely to have an identifiable etiology compared with chronic urticaria; however, no etiology can be found in 30 to 50 percent of patients [7].
Theories of pathogenesis for chronic urticaria are described elsewhere. (See "Chronic spontaneous urticaria: Clinical manifestations, diagnosis, pathogenesis, and natural history", section on 'Theories of pathogenesis'.)
Infections — Viral, bacterial, and parasitic infections are associated with new-onset urticaria, particularly in children.
●Viral and bacterial infections – Infections are associated with over 80 percent of cases of acute urticaria in some pediatric series [2,8-11]. Acute urticaria may develop during or following a viral or bacterial infection; in some cases, urticaria can appear several weeks after resolution of the acute symptoms. Immune activation, involving immune complex formation and/or complement activation, is a proposed mechanism of mast cell activation, although the exact pathogenesis is unclear.
Specific infections that have been associated with urticaria include:
•Common respiratory viruses [7,8,12-14]:
-Picornavirus
-Common coronaviruses
-Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)
-Respiratory syncytial virus (RSV)
-Adenovirus
•Bacterial infections:
-Mycoplasma pneumoniae [15,16]
-Urinary tract infections [8]
●Parasitic infections – Parasitic infections generally cause acute, self-limited urticaria in association with prominent peripheral blood eosinophilia [17].
•Infections with Ancylostoma, Strongyloides, Filaria, Echinococcus, Trichinella, Toxocara, Fasciola, Schistosoma mansoni, and Blastocystis hominis have all been associated with urticaria. Stool examination is probably only indicated in travelers to endemic areas and in patients with peripheral blood eosinophilia. (See "Approach to the patient with unexplained eosinophilia".)
•Ingestion of fish contaminated with the parasite Anisakis simplex can also cause urticaria. Anisakis can be transmitted through the ingestion of sushi [18]. (See "Seafood allergies: Fish and shellfish", section on 'Anisakis'.)
Medications — Many medications have the potential to cause urticaria due to activation of mast cells by IgE, nonimmunologic activation through the receptor Mas-related G protein–coupled receptor member X2 (MRGPRX2), or through other mechanisms. When urticaria develops in response to a drug, symptoms may appear within minutes (typical of intravenous [IV] administration) to an hour or two (oral administration). (See "Mast cells: Surface receptors and signal transduction", section on 'Activating receptors'.)
Medications that frequently cause urticaria include:
●Beta-lactam antibiotics – Beta-lactam antibiotics include penicillins and cephalosporins; these usually cause urticaria through an IgE-mediated reaction. (See "Penicillin allergy: Immediate reactions".)
●Fluoroquinolones – Fluoroquinolones usually cause urticarial reactions through MRGPRX2, although rare IgE-mediated reactions are also possible. (See "Hypersensitivity reactions to fluoroquinolones", section on 'Immediate reactions'.)
●Anesthetic muscle relaxants – Anesthetic muscle relaxants, including atracurium, vecuronium, and succinylcholine, may cause urticaria either through MRGPRX2 or via IgE-mediated reactions. (See "Perioperative anaphylaxis: Allergy evaluation and prevention of recurrent reactions", section on 'Neuromuscular-blocking agents'.)
●Vancomycin – Vancomycin infusion reaction is seen after rapid vancomycin infusion and usually presents as diffuse erythema or flushing and, less commonly, with accompanying urticaria. Vancomycin activates mast cells through MRGPRX2 in most cases. The concomitant use of opiates and vancomycin may increase the likelihood of a reaction. (See "Vancomycin hypersensitivity".)
●Opioids – Opiate analgesics, such as morphine and codeine, can activate mast cells, and patients are variably sensitive to this effect. Most patients will develop mild pruritus with high-dose opioids, but some will develop frank urticaria. Dextromethorphan, an opiate derivative ingredient in cough suppressant syrups, can also cause urticaria through this mechanism [19]. (See "Perioperative anaphylaxis: Allergy evaluation and prevention of recurrent reactions", section on 'Opioids'.)
●NSAIDs – Nonsteroidal antiinflammatory drugs (NSAIDs) can cause urticaria and/or angioedema in some patients. Patients or caregivers may not recognize the association until it has occurred several times. (See "NSAIDs (including aspirin): Allergic and pseudoallergic reactions".)
Foods and certain food additives — IgE-mediated allergic reactions to foods can cause urticaria, typically within 30 minutes of ingestion. Milk, eggs, peanuts, tree nuts, soy, and wheat are the most common foods to cause generalized urticaria in children. Food allergies can also develop in adulthood, even in patients who previously tolerated that food; this most commonly occurs due to fish and shellfish [20]. In Mediterranean areas, peach allergy can develop in adulthood [21]. (See "Clinical manifestations of food allergy: An overview".)
Although patients often suspect synthetic additives in commercially prepared foods as a possible culprit, they are believed to be a relatively rare cause of urticarial reactions. In contrast, certain natural food additives, such as the orange food dye annatto (derived from the seeds of the achiote tree) and the red dye carmine red (derived from insects), have been well-documented causes of urticaria and anaphylaxis. Adverse reactions to food additives are discussed in detail elsewhere. (See "Allergic and asthmatic reactions to food additives".)
Contact urticaria — Contact urticaria can occur due to IgE-mediated or non-IgE-mediated causes. Urticaria due to direct skin contact with an allergen usually affects just the skin that touches the substance.
●Contact with allergens - Physical contact with a number of allergens may result in IgE-mediated urticaria, including plant products and resins, raw fruits and vegetables, or raw seafood [22]. People employed in food processing can develop contact urticaria on the hands, arms, and face from various exposures [23]. Children sometimes develop urticaria upon contact with animal saliva (eg, dog or cat) if allergic to those allergens.
●Latex allergy - Occupational, recreational, dental, or surgical exposure to latex may cause IgE-mediated urticaria, angioedema, asthma, or anaphylaxis in susceptible individuals [24]. Everyday scenarios in which patients may be exposed to significant amounts of latex include inflation of balloons and use of latex gloves. High-risk patients include health care workers and food service workers if using gloves or other equipment containing latex, although this is far less common than in previous decades. (See "Latex allergy: Epidemiology, clinical manifestations, and diagnosis".)
●Stinging nettle – The nettle plant (Urtica dioica), after which the disorder "urticaria" was named, is a common weed found in Europe, North and South America, and parts of Africa that causes hives and a stinging sensation immediately following contact with the skin [25-27]. These symptoms may be due to histamine in the nettle plant itself, in addition to mediators that cause pain [28].
In contrast, detergents, soaps, and lotions rarely cause urticaria; they are more likely to cause contact dermatitis. Similarly, inhalation of animal danders, pollens, or molds typically causes rhinitis or bronchospasm rather than isolated urticaria. (See "Allergic contact dermatitis: Clinical features and diagnosis" and "Allergic contact dermatitis in children".)
Physical stimuli — Mast cells can also be activated by physical stimuli (see "Mast cells: Surface receptors and signal transduction", section on 'Receptors for mechanical stimulation'). Physical urticarial syndromes are forms of chronic urticaria that are triggered by specific physical factors, such as sudden changes in body temperature, pressure, stroking, or vibration against the skin; exercise; exposure to sunlight, cold, or water; or other stimuli (table 2). These disorders are reviewed separately. (See "Physical (inducible) urticaria" and "Cold urticaria".)
Other transient causes — Additional transient causes of urticaria include:
●COVID-19 vaccines and boosters – Urticaria with or without angioedema has been reported in association with coronavirus disease 2019 (COVID-19) messenger ribonucleic acid (mRNA) vaccines and boosters, particularly the Moderna mRNA booster [29,30]. In a study of over 800 patients in two cohorts with newly diagnosed urticaria that had occurred most days of the week and persisted for weeks to months, 92 and 94 percent of cases were temporally associated with receiving the Moderna vaccine or booster [30]. Onset of urticaria was between 8 and 13 days after vaccination. In those patients with subsequent resolution, the duration of symptoms ranged from two to six months. The author and editors of this topic have also observed reactivation of chronic urticaria that had been quiescent for years. (See "COVID-19: Cutaneous manifestations and issues related to dermatologic care", section on 'Cutaneous adverse events'.)
●Stinging and biting insects – Stinging insects that can cause true urticarial lesions as part of an IgE-mediated allergic reaction include Hymenoptera (eg, bees, wasps, hornets, and stinging ants) and Triatoma (eg, kissing bugs). (See "Bee, yellowjacket, wasp, and other Hymenoptera stings: Reaction types and acute management" and "Reactions to bites from kissing bugs (primarily genus Triatoma)" and "Bedbugs".)
●Radiocontrast medium – Radiocontrast agents are associated with urticaria and angioedema. (See "Diagnosis and treatment of an acute reaction to a radiologic contrast agent".)
●Scombroid syndrome – The ingestion of poorly preserved fish (tuna in most cases, but sometimes mackerel or sardines) containing large amounts of histamine may cause acute symptoms that resemble those of an IgE-mediated allergic reaction characterized by flushing, urticaria, diarrhea, headache, and sometimes bronchospasm. Symptoms may appear from a few minutes to up to one to two hours after ingestion depending on the concentration of histamine in the fish, the quantity ingested, and the association with other foods. (See "Scombroid (histamine) poisoning".)
Systemic disorders that may include urticaria — Uncommonly, urticaria or urticaria-like lesions may be an early feature of systemic disorders. The urticaria associated with systemic disorders is usually recurrent, persistent, and relatively difficult to treat, but information is limited when symptoms first develop. Because most patients will prove to have transient symptoms and no underlying systemic disease, we ask about other symptoms but balance those questions with reassurance. Clinical features that can help distinguish these disorders from uncomplicated chronic urticaria are reviewed separately. (See "Chronic spontaneous urticaria: Clinical manifestations, diagnosis, pathogenesis, and natural history", section on 'Differential diagnosis'.)
●Serum sickness – Serum sickness to exogenous proteins or and serum sickness-like reactions (SSLRs) to medications or viral infections may present with an urticarial rash accompanied by fever, polyarthralgias, polyarthritis, and/or lymphadenopathy. The urticarial lesions of serum sickness and SSLRs often have a violaceous hue (picture 4A-B). These reactions typically develop within one to three weeks after administration of the causative agent. Proteinuria, edema, and abdominal pain may also be present. These reactions are discussed elsewhere. (See "Serum sickness and serum sickness-like reactions".)
●Cutaneous small vessel vasculitis – Vasculitis should be suspected when individual urticarial lesions are painful rather than pruritic, last longer than 24 to 36 hours, appear purpuric or ecchymotic, or leave residual ecchymosis or hyperpigmentation upon resolution (in the absence of trauma from scratching) (table 3 and picture 5 and picture 6 and picture 7). Vasculitis should also be suspected in patients with urticaria accompanied by fever, arthralgias, arthritis, weight changes, or lymphadenopathy. Specific examples include:
•Urticarial vasculitis – Urticarial vasculitis is a disorder characterized by urticarial lesions with vasculitic findings on skin biopsy (picture 6). Urticarial vasculitis may be a cutaneous or systemic disease, and it may occur in the setting of another rheumatologic disorder or, rarely, a malignancy. (See "Urticarial vasculitis" and "Cutaneous manifestations of internal malignancy".)
•IgA vasculitis (Henoch-Schönlein purpura) – Immunoglobulin A (IgA) vasculitis is a systemic vasculitis with a prominent cutaneous component characterized by purpuric lesions, particularly involving the lower extremities. The skin lesions can be urticarial initially, although the development of systemic disease with arthralgias, abdominal pain, and kidney involvement should prompt investigation for this condition. (See "IgA vasculitis (Henoch-Schönlein purpura): Clinical manifestations and diagnosis", section on 'Skin manifestations'.)
Cutaneous small vessel vasculitides are discussed in detail elsewhere. (See "Overview of cutaneous small vessel vasculitis".)
●Mastocytosis – Mastocytosis and mast cell disorders are rare conditions in which patients present with apparent allergic reactions and anaphylaxis to a variety of triggers. Characteristic skin findings are helpful in diagnosis. These disorders are reviewed separately. (See "Mastocytosis (cutaneous and systemic) in adults: Epidemiology, pathogenesis, clinical manifestations, and diagnosis".)
●Autoimmune conditions – Urticaria may be a presenting manifestation or occur sporadically over time in patients with autoimmune conditions [31]. The etiology of this remains unclear but may be due to direct mast cell activation via complement receptors or due to the generation of autoantibodies that may result in anaphylactoid degranulation. Specific associated conditions include:
•Autoimmune thyroid disease
•Systemic lupus erythematosus
•Rheumatoid arthritis
•Sjögren's disease
•Celiac disease
Screening for these disorders in the setting of an acute episode of urticaria is not indicated unless there are other preceding symptoms that suggest that one of these disorders may be present.
●Malignancies – Uncommonly, urticaria may be seen with malignancies, especially immunoglobulin M (IgM) and sometimes immunoglobulin G (IgG) paraproteinemias. The pathogenesis is unclear but may be due to complement-mediated pathways. In these cases, the urticaria is persistent and becomes chronic. (See "Chronic spontaneous urticaria: Clinical manifestations, diagnosis, pathogenesis, and natural history", section on 'Unclear association with malignancy'.)
EVALUATION AND DIAGNOSIS
Clinical history and exam — The primary goals of the clinical history are to exclude serious disorders and identify potential etiologies of the urticaria (algorithm 1). The physical examination is necessary to confirm characteristic lesion features. If the patient has no lesions at the time of evaluation, showing patients photographs of urticaria and asking if their lesions look similar can be helpful (picture 1).
Conditions to exclude — Most new-onset urticaria is benign and self-limited. We use the clinical history and exam to help identify those rare patients in whom urticaria is a manifestation of a more serious underlying etiology. Patients with new-onset urticaria who do not endorse systemic symptoms on a thorough review of systems do not need additional evaluation for these disorders.
Specific conditions to exclude via history and physical examination include:
●Anaphylaxis – It is not uncommon for patients to present to the emergency department with anaphylaxis that is not fully appreciated by clinicians and labeled as simple urticaria. Skin changes are obvious to patients and providers, but patients may not report more subtle symptoms unless specifically asked, especially if they have resolved. In patients who present with new-onset urticaria that began within the previous few hours, it is important to ask about other signs and symptoms of a generalized allergic reaction or anaphylaxis, including chest tightness, difficulty breathing, hoarse voice of throat tightness, nausea, vomiting, crampy abdominal pain, or lightheadedness (table 4). Any patient suspected of anaphylaxis should be treated accordingly and equipped with epinephrine for self-administration. (See "Anaphylaxis: Acute diagnosis".)
●Urticarial vasculitis – As described above, urticarial lesions are intensely pruritic and resolve within 24 hours without leaving residual ecchymosis or hyperpigmentation. In contrast, lesions of urticarial vasculitis are painful or burning, last longer than 24 hours, and often leave residual bruising on resolution (table 3). If the patient is unsure of the duration of the lesions, a lesion can be circled with a pen and time to resolution noted. Any features of urticarial vasculitis should prompt laboratory evaluation and skin biopsy, as discussed below. (See 'Limited role for additional testing' below.)
●Systemic disorders – We ask patients about any symptoms that might indicate an associated systemic disorder, including thyroid-related symptoms, unexplained fever, weight loss, arthralgias, and arthritis [32,33]. We also assess for lymphadenopathy. Rarely, new-onset urticaria can be associated with systemic disorders, and patients with compatible symptoms should be evaluated for the appropriate conditions. (See 'Systemic disorders that may include urticaria' above.)
Questions about possible causes — Once anaphylaxis, urticarial vasculitis, and systemic disorders are determined to be unlikely, we assess for transient factors that may have caused urticaria (table 1) (see 'Etiologies and pathophysiology' above). In addition, it is helpful to ask whether the patient has had hives in the past. Some children develop acute urticaria repeatedly with infections.
We ask the patient to review events in the hours before the urticaria appeared. We specifically ask about:
●Infectious symptoms or risk factors for new infections (eg, recent illnesses, travel)
●New medications or supplements (either in the preceding days or week or within the few hours before lesions appeared)
●Insect stings (eg, bees, wasps, stinging ants) or bites (eg, kissing bugs)
●Newly introduced foods, especially in infants and young children
●Associated exercise or physical triggers (sunlight, water, vibration)
●Temperature extremes or shifts in body temperature (eg, cooling after a hot shower)
When to suspect an IgE-mediated cause — Immunoglobulin E (IgE) mediated reactions should be suspected if urticaria occurs within minutes to two hours after exposure to a potential allergen. Common allergens that trigger IgE-mediated urticaria include antibiotics (particularly beta-lactams), certain foods (eg, peanuts, tree nuts, or shellfish), and some types of insects (eg, bees, wasps, fire ants). This can occur even if the patient previously tolerated the allergen without a reaction.
It is important to recognize IgE-mediated causes because there is a risk of developing a systemic reaction and anaphylaxis on subsequent exposure. Patients should be advised to avoid the potential cause until further evaluation by a specialist. For example, a child who develops generalized urticaria immediately after ingesting peanut butter should not be given it again until they are evaluated for peanut allergy. (See 'Considerations for specialty referral' below.)
Establishing the diagnosis — Urticaria is diagnosed clinically based on a detailed history and physical examination confirming the presence of characteristic skin lesions [34-37]. Lesions (or photographs of the patient's lesions) should be visualized directly to make the diagnosis with certainty since the term "hives" is used nonspecifically by patients. If there are no active lesions at the time of evaluation, stroking the skin may be able to reproduce an urticarial response and help establish the diagnosis (dermatographism). However, the absence of this response does not exclude urticaria. (See "Physical (inducible) urticaria", section on 'Dermographism'.)
Urticaria are pruritic, circumscribed, raised, and erythematous and can vary dramatically in size and intensity of erythema (picture 1). Of note, erythema may be difficult to appreciate on highly pigmented skin (picture 8A-B). Individual lesions resolve within 24 hours. Some patients may present with angioedema, which is nondependent swelling of the skin with poorly defined borders and varying degrees of erythema (picture 3). Patients may have urticaria alone, urticaria and angioedema, or angioedema alone. In most patients, laboratory tests are not needed to confirm the diagnosis.
Limited role for additional testing — For most patients with new-onset urticaria, laboratory tests are not helpful. Two-thirds of cases will resolve spontaneously without any long-term sequelae. We limit laboratory evaluation only to patients who have features suggestive of urticarial vasculitis, a specific allergy, or an underlying systemic disorder; this is consistent with international, European, and British practice parameters [38-40]. In contrast, American practice parameters state that a limited evaluation "may be considered" in all cases of new-onset urticaria, primarily for the purpose of detecting underlying disorders earlier in the one-third of patients who will develop chronic urticaria [41]. (See "Chronic spontaneous urticaria: Clinical manifestations, diagnosis, pathogenesis, and natural history", section on 'Laboratory evaluation'.)
There are specific, limited situations in which we do obtain additional evaluation for patients with new-onset urticaria. These include patients in whom there is suspicion for:
●Treatable infection – If the patient has symptoms and/or risk factors compatible with an infection that would warrant treatment, we perform the appropriate evaluation (eg, influenza testing in a patient in whom there is suspicion and results would alter management, stool testing in a patient with symptoms and risk factors for a parasitic infection). Testing for common respiratory viruses is not necessary for urticaria alone unless it would otherwise be indicated. (See "Bronchiolitis in infants and children: Clinical features and diagnosis", section on 'Viral testing'.)
●Urticarial vasculitis – For patients who have lesion features suggestive of vasculitis (table 3), we obtain laboratory evaluation as well as lesion biopsy. Initial laboratory evaluation includes complete blood count with differential, serum creatinine, erythrocyte sedimentation rate, and complement studies (usually C3 and C4). (See "Urticarial vasculitis".)
●Systemic disorder – For patients who endorse systemic symptoms (eg, unintentional weight loss, arthralgias) on review of symptoms, we initiate a workup (usually starting with laboratory evaluation) to evaluate the specific symptom.
●IgE-mediated allergy – For patients who have a suspected IgE-mediated allergy, serum tests for one or a small number of allergen-specific IgE antibodies are appropriate. This should only be done if the history suggests a possible allergic cause. Sending large panels of specific IgE tests to "screen" for allergies is costly and unlikely to yield useful information. (See 'When to suspect an IgE-mediated cause' above.)
However, interpretation of serum testing results depends on the clinical context and often requires expertise. A positive result is suggestive, although not diagnostic, of an allergy, and a negative result does not definitively exclude allergy. Because of this, in many cases, referral to an allergist for further evaluation is appropriate. For example, if there is a high clinical suspicion for an IgE-mediated allergy (eg, recurrent generalized urticaria developing within minutes after exposure to a specific food), skin testing would be appropriate even if there is a negative serum test. Additionally, if the results of serum testing have important patient implications (eg, the results show an allergy to a food that the patient commonly eats), skin testing can be helpful to confirm the diagnosis and ensure the patient does not avoid the food needlessly. (See 'Considerations for specialty referral' below and "Overview of in vitro allergy tests".)
In addition, patients with chronic urticaria (ie, patients with symptoms most days of the week that have been ongoing for six weeks or longer) as well as those with isolated angioedema warrant laboratory evaluation. These are discussed separately. (See "Chronic spontaneous urticaria: Clinical manifestations, diagnosis, pathogenesis, and natural history", section on 'Laboratory evaluation' and "An overview of angioedema: Clinical features, diagnosis, and management", section on 'Isolated angioedema'.)
DIFFERENTIAL DIAGNOSIS —
The conditions discussed in this section may mimic various features of urticaria [42]. The presence or absence of pruritus is a helpful clinical feature that can be used to narrow the differential.
Pruritic conditions — Pruritic conditions that are more likely to be confused with urticaria are discussed here. An overview of the causes of pruritic dermatoses is found separately. (See "Pruritus: Etiology and patient evaluation".)
●Atopic dermatitis – Atopic dermatitis is a common disorder that presents initially as intensely pruritic erythematous patches with papules and some scaling. In infants, the face, scalp, extremities, or trunk are typically involved, while the diaper area is spared. In older children and adults, the flexural areas (neck, antecubital fossae, and popliteal fossae) are most commonly involved. Other sites include the face, wrists, and forearms (picture 9). Erythematous areas of involvement last for days or weeks and have ill-defined borders. Scaling and xerosis develop with time. (See "Atopic dermatitis (eczema): Pathogenesis, clinical manifestations, and diagnosis".)
●Contact dermatitis – Contact dermatitis refers to any dermatitis arising from direct skin exposure to a substance. The dermatitis may either be allergic or irritant induced. The latter is more common. Contact dermatitis is an erythematous, papular dermatitis, often with areas of vesiculation (picture 10). It is distributed in the areas of direct contact. (See "Allergic contact dermatitis in children" and "Irritant contact dermatitis in adults" and "Common allergens in allergic contact dermatitis".)
●Drug eruptions – Drug eruptions, also called morbilliform or exanthematous drug eruptions, are cutaneous drug reactions that closely mimic viral exanthems but occur in association with a medication. These dermatoses may or may not be pruritic and begin as small macules and/or papules that become larger and confluent with time (picture 11). The individual lesions are persistent, unlike urticaria. (See "Drug eruptions".)
●Bullous pemphigoid – Bullous pemphigoid is an autoimmune blistering condition that primarily affects adults over 60 years of age and may start with pruritus, with or without urticarial lesions. Blistering frequently becomes evident eventually (picture 12), although rare patients with only pruritus or urticarial lesions have been described. (See "Clinical features and diagnosis of bullous pemphigoid and mucous membrane pemphigoid", section on 'Clinical features of bullous pemphigoid'.)
●Erythema multiforme minor – Erythema multiforme minor is a syndrome characterized by erythematous, iris-shaped macules and vesiculobullous lesions with a target appearance (picture 13). The lesions may be painful or pruritic and distributed symmetrically on the extensor surfaces of the extremities (particularly the palms and soles). Individual lesions last several days, unlike urticaria. There may be accompanying fever and malaise. (See "Erythema multiforme: Pathogenesis, clinical features, and diagnosis".)
●Plant-induced reactions – Poison ivy and poison oak can present with urticaria-like lesions initially that evolve into vesicular lesions. (See "Poison ivy (Toxicodendron) dermatitis".)
Nonpruritic conditions — Nonpruritic conditions that may resemble acute urticaria include viral exanthems and Sweet syndrome.
●Viral exanthems – Viral exanthems are common in children and can occur with many different infections, including erythema infectiosum (fifth disease), Epstein-Barr virus, enteroviruses, and measles. However, viral exanthems are generally not pruritic and usually consist of erythematous maculopapular eruptions that persist for days. Fever is often present. The macules are relatively fixed compared with urticarial lesions, which continually change, with new lesions appearing as older lesions resolve.
●Sweet syndrome – Sweet syndrome is an uncommon disease characterized by recurrent episodes of painful, long-lasting inflammatory papules and plaques associated with fever, arthralgias, and peripheral leukocytosis (picture 14). There may be a history of a febrile illness one to three weeks before the onset of skin lesions in some cases. (See "Sweet syndrome (acute febrile neutrophilic dermatosis): Pathogenesis, clinical manifestations, and diagnosis".)
MANAGEMENT
Patient counseling and reassurance — We reassure patients with new-onset urticaria that this is an extremely common condition that affects up to 20 percent of people at some point. A specific cause is often not found, and, in approximately two-thirds of patients, urticaria will resolve with or without treatment within six weeks. Among patients whose symptoms resolve within six weeks, approximately half improve within one week, 75 percent within two weeks, and 90 percent within three weeks [43].
Even for patients who go on to develop chronic urticaria, no underlying disease is found in most patients, and the disorder is often self-limited. (See "Chronic spontaneous urticaria: Clinical manifestations, diagnosis, pathogenesis, and natural history", section on 'Natural history and prognosis'.)
H1 antihistamine therapy for all patients — Initial pharmacologic treatment of new-onset urticaria (with or without angioedema) is intended to provide short-term relief of symptoms. The literature on management of acute urticaria is sparse, probably because the condition is usually self-limited [44].
Second-generation antihistamines preferred — In most situations, we prefer newer second-generation H1 antihistamines (eg, cetirizine, bilastine [not available in the US]) over older, first-generation agents. The newer drugs are similarly effective and minimally sedating, with fewer anticholinergic adverse effects and more convenient dosing [45-50]. Second-generation H1 antihistamines are recommended as first-line therapy by published guidelines from both allergy and dermatology expert panels [51,52]. Specific options with adult and pediatric dosing are shown in the table (table 5).
The only trial directly comparing first- to second-generation H1 antihistamines for acute urticaria compared diphenhydramine (50 mg) to cetirizine (10 mg), both given intravenously (IV) in the emergency department setting [53]. Symptom reduction at two hours was equivalent, with less sedation with cetirizine.
We know of no data demonstrating that any specific second-generation antihistamine is more effective than another for the treatment of acute urticaria, although a few studies in patients with chronic urticaria suggest that cetirizine and levocetirizine may be modestly more effective than other agents. (See "Chronic spontaneous urticaria: Standard management and patient education", section on 'Agents and efficacy studies'.)
Dosing and administration — We typically initiate antihistamines at standard dosing, but many patients require increased dosing for symptom control. In most cases, oral formulations are appropriate, but parenteral formulations may be preferred when rapid onset of action is necessary.
●Dosing – We usually start antihistamines at standard dosing and advise patients they can double or triple the dose if necessary (table 5). Some patients require higher-than-standard doses for control of urticarial symptoms. Doses up to four times the standard have been studied in chronic hives and have been shown to be safe and well-tolerated. (See "Chronic spontaneous urticaria: Standard management and patient education", section on 'H1 antihistamines'.)
●Formulation – If rapid onset of action is desired, parenteral agents can be used. Several H1 antihistamines are available in parenteral formulations:
•Cetirizine – The dose of cetirizine is 10 mg IV administered over one to two minutes. Children 6 months to 5 years may receive 2.5 mg every 24 hours, those 6 to 11 years may receive 5 to 10 mg every 24 hours, and those 12 and older may receive 10 mg every 24 hours.
•Diphenhydramine – The dose of diphenhydramine in adults is 25 to 50 mg given by slow IV administration or intramuscular (IM) injection every four to six hours as needed. Children may receive 0.5 to 1.25 mg/kg (up to 50 mg per dose) IV/IM every six hours as needed.
•Hydroxyzine – The dose of hydroxyzine in adults is 25 to 50 mg deep IM administration in adults every six hours as needed. Do not administer IV. Children may receive 0.5 to 1 mg/kg (up to 50 mg per dose) IM every six hours as needed.
Note that, although one trial showed that IV cetirizine (10 mg) controlled symptoms equivalently to IV diphenhydramine (50 mg) and caused less sedation, cetirizine is the only nonsedating antihistamine available in a parenteral formulation, and it is costly (approximately $400 versus <$4 per dose in one US online drug pricing tool [54]) and not widely available.
Duration of treatment — We advise continuing H1 antihistamine treatment until the lesions completely resolve. In some patients, treatment with H1 antihistamines results in clearance of the lesions, but, in others, treatment may only achieve flattening of the lesions and reduction in pruritus, with persistence of flat erythematous macules.
●Resolution – Once no new lesions have appeared for a day or two, patients may taper down and stop the antihistamines. Patients who are taking more than once-daily antihistamines should gradually taper their dose over several days because some patients experience rebound symptoms if antihistamines are stopped abruptly, particularly with cetirizine [55].
●Continued symptoms – If patients continue to have recurrent episodes of hives most days of the week for six weeks, they very likely are developing chronic urticaria. Initial therapy for chronic urticaria is high-dose nonsedating antihistamines (eg, cetirizine 20 mg twice daily or levocetirizine 10 mg twice daily). High-dose antihistamine therapy is discussed in detail elsewhere. (See "Chronic spontaneous urticaria: Standard management and patient education", section on 'Up-dosing of second-generation agents'.)
Pregnancy and lactation — Pregnant patients may be treated initially with cetirizine (10 mg once daily) or loratadine (10 mg once daily). There are reassuring human data for each of these drugs in a large number of pregnant patients [56]. They are also minimally excreted in breast milk and should not cause sedation or poor feeding in the infant. Other second-generation agents are likely also safe, but there are fewer studies available. The first-generation agent chlorpheniramine, 4 mg orally every four to six hours, may also be safely used in pregnancy [57,58]. Safety issues surrounding the use of antihistamines in pregnancy are reviewed separately. (See "Recognition and management of allergic disease during pregnancy", section on 'Oral antihistamines'.)
First-generation antihistamines — The first-generation antihistamines include diphenhydramine, chlorpheniramine, and hydroxyzine [59]. These agents are lipophilic and readily cross the blood-brain barrier, causing sedation and impairment of performance (eg, driving skills and reaction times) in more than 20 percent of patients. Although they are no more effective than newer antihistamines for control of urticaria and pruritus in chronic urticaria, the sedation may be viewed as helpful by some patients [60]. Patients should be warned to avoid driving or operating machinery [61]. In addition, anticholinergic side effects are also problematic and include dry mouth, diplopia, blurred vision, urinary retention, or vaginal dryness. Finally, there is a probable small increase in seizure risk in young children [62]. For these reasons, we avoid first-generation antihistamines in young children and older adults. However, despite the adverse effects, young, healthy adults may find a sedating H1 antihistamine at bedtime helpful, especially when combined with a nonsedating H1 antihistamine during the day.
Adjunctive glucocorticoids for persistent symptoms — Glucocorticoids are probably overprescribed in acute urticaria. We reserve glucocorticoids for patients who have persistent symptoms or prominent angioedema after several days of regularly administered H1 antihistamines. Glucocorticoids do not inhibit mast cell degranulation directly but may act by suppressing a variety of contributing inflammatory mechanisms.
The optimal agent and dose have not been determined for acute urticaria. If given, we typically administer:
●For adults – Prednisone 30 to 60 mg daily, with tapering of the dose over five to seven days
●For children – Prednisolone 0.5 to 1 mg/kg/day (maximum 60 mg daily), with tapering of the dose over five to seven days
Antihistamine therapy should be continued during and after the course of glucocorticoids because some patients experience an exacerbation as the glucocorticoids are tapered or discontinued. If symptoms do not recur over several days after stopping glucocorticoids, then antihistamines can be discontinued. For patients whose symptoms recur when medications are discontinued, antihistamines should be reinstituted and used at the lowest effective dose. Repeated courses of glucocorticoids should be avoided as the risks of adverse effects outweigh the benefits for most patients.
Our guidance is based primarily on clinical experience as the data on the use of glucocorticoids for urticaria are conflicting. As an example, in a systematic review, the addition of prednisone to an antihistamine (levocetirizine or cetirizine) did not improve symptoms of acute urticaria compared with antihistamine alone in two out of three randomized trials [63]. However, a separate meta-analysis found that glucocorticoids added to antihistamines did improve urticaria activity and itch score, but with increased adverse effects [64].
Therapies we do not recommend
●H2 antihistamines – We do not routinely use H2 antihistamines in the treatment of new-onset urticaria, as high-quality studies have not evaluated them in this population and their benefit is uncertain [65]. One potential exception is in cases of severe symptoms when IV formulations are available; two small randomized trials have shown adding IV H2 antihistamines to IV H1 antihistamines may lead to more rapid symptom resolution, although these studies had methodologic limitations [66,67].
The role of H2 blockers in chronic urticaria is discussed elsewhere. (See "Chronic spontaneous urticaria: Standard management and patient education", section on 'H2 antihistamines'.)
●Topical agents – We do not routinely advise topical agents (eg, antihistamines or corticosteroids) in the treatment of urticaria, as there is no evidence that they are beneficial in either lesion resolution or relief of pruritus.
CONSIDERATIONS FOR SPECIALTY REFERRAL —
Patients with new-onset urticaria warrant referral to a specialist in the following situations:
●There is concern for urticarial vasculitis. Patients should be referred to a dermatologist or another specialist able to perform a skin biopsy. (See 'Conditions to exclude' above.)
●There is suspicion for an IgE-mediated allergic cause. The allergy specialist will evaluate for possible causes and may perform testing to confirm the triggers. In cases of anaphylaxis, they may equip the patient with epinephrine for self-administration and educate about allergen avoidance. These issues are discussed in detail separately. (See "Anaphylaxis: Emergency treatment", section on 'Discharge care'.)
●Symptoms are difficult to control, require repeated glucocorticoid courses, or persist beyond six weeks. These patients can be referred to a dermatology or allergy specialist to escalate their antihistamine regimen and consider biologic agents or immunosuppressants if symptoms become chronic and severe. (See "Chronic spontaneous urticaria: Standard management and patient education", section on 'Stepwise approach to treatment'.)
PROGNOSIS —
Two-thirds of cases of new-onset urticaria will prove self-limited within six weeks, regardless of whether an underlying cause is identified. Among patients whose symptoms resolve within six weeks, approximately half will improve within one week, 75 percent within two weeks, and 90 percent within three weeks [43].
The remaining one-third of patients will go on to develop chronic urticaria. The prognosis of chronic urticaria is reviewed in detail elsewhere. (See "Chronic spontaneous urticaria: Clinical manifestations, diagnosis, pathogenesis, and natural history", section on 'Natural history and prognosis'.)
SOCIETY GUIDELINE LINKS —
Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Urticaria and angioedema (excluding hereditary angioedema)".)
INFORMATION FOR PATIENTS —
UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topic (see "Patient education: Hives (The Basics)")
●Beyond the Basics topic (see "Patient education: Hives (urticaria) (Beyond the Basics)")
SUMMARY AND RECOMMENDATIONS
●Prevalence and description – Urticaria (also called hives or wheals) affects up to 20 percent of the population at some point in their lives. Urticarial lesions are intensely pruritic, circumscribed, raised, erythematous plaques, often with central pallor (picture 8B-C). Morphology and size can vary (picture 1). Individual urticarial lesions typically develop over minutes to hours and resolve in hours to a day without residual markings. There may be accompanying angioedema, which is swelling deeper in the skin. (See 'Epidemiology' above and 'Clinical manifestations' above.)
●Acute versus chronic – Acute urticaria is defined as periodic outbreaks of urticarial lesions that stop occurring within six weeks. Urticaria that persists beyond six weeks (with signs or symptoms occurring most days of the week) is classified as chronic. The lesions of acute and chronic urticaria are identical in appearance, so when the problem first develops, it is not possible to differentiate the two disorders. (See 'Acute versus chronic' above.)
●Possible etiologies of new-onset urticaria – Common etiologies of urticaria include infections, medications, foods, contact allergens, and physical stimuli (table 1). Rarely, acute urticaria can be due to underlying systemic disorders. No cause is identified in up to half of cases. (See 'Etiologies and pathophysiology' above.)
●Evaluation and diagnosis – Urticaria is diagnosed clinically based on the presence of circumscribed, raised, erythematous plaques that are intensely pruritic. Individual lesions are transient, usually appearing and enlarging over the course of minutes to hours and then disappearing within 24 hours. We obtain a detailed history to exclude anaphylaxis, urticarial vasculitis, and systemic disorders (algorithm 1). These conditions occur in a small minority of patients with urticaria. We also ask directed questions to help identify possible causes of the urticaria, including recent illnesses or exposure to potential allergens. For most patients, no laboratory evaluation is necessary. (See 'Evaluation and diagnosis' above.)
●Management – The management of new-onset urticaria depends on severity and associated angioedema.
•Reassurance – We reassure patients that urticaria is a common condition, and, although a specific cause is often not found, the symptoms resolve spontaneously in most people within days to a few weeks. (See 'Patient counseling and reassurance' above.)
•H1 antihistamines for all patients – In all patients with new-onset urticaria who seek symptom relief, we suggest treatment with a nonsedating H1 antihistamine rather than sedating antihistamines (Grade 2B) (table 5). These agents are equally efficacious with fewer side effects. We usually start H1 antihistamines at standard dosing and advise patients they can double or triple the dose if necessary. Some patients may require higher-than-standard doses (eg, cetirizine 10 mg twice daily) for symptom control. (See 'H1 antihistamine therapy for all patients' above.)
•Adjunctive glucocorticoids for persistent symptoms – For patients with persistent symptoms or prominent angioedema after several days of H1 antihistamine treatment, we suggest adding a brief course of oral glucocorticoids (Grade 2C). We typically prescribe prednisone 30 to 60 mg daily in adults or prednisolone 0.5 to 1 mg/kg/day in children, tapered over five to seven days, while antihistamines are continued. (See 'Adjunctive glucocorticoids for persistent symptoms' above.)
●Prognosis – Two-thirds of cases of urticaria (with or without angioedema) prove to be self-limited, resolving in days to a few weeks. Urticarial outbreaks that continue to occur after six weeks are classified as chronic. Patients with difficult-to-control symptoms that are persistent can be referred to an allergy or dermatology specialist. (See 'Prognosis' above and 'Considerations for specialty referral' above.)
ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Clifton O Bingham, III, MD, who contributed to earlier versions of this topic review.
