Patient education: Hives (urticaria) (Beyond the Basics)

HIVES OVERVIEW — "Urticaria" is the medical term for hives. Hives are raised or puffy areas of the skin that itch intensely (picture 1). Hives are a very common condition. About 20 percent of people have hives at some time during their lives.

Hives develop when there is a reaction that activates immune cells in the skin called mast cells. When activated, these cells release natural chemicals. One important chemical is histamine, which causes itching, redness, and swelling of the skin in an area: a hive. In most cases, hives appear suddenly and disappear within several hours.

Hives usually respond well to treatment, which includes medicines and avoiding whatever triggered the hives.

More detailed information about hives is available by subscription. (See 'Professional level information' below.)

HIVES SYMPTOMS

Skin appearance — Hives are raised areas that itch intensely (picture 1). Hives might look reddish in color on light-colored skin. The color changes can be hard to see on darker skin (picture 2). In some cases, the raised areas enlarge and merge together (picture 3). Itching is usually the most bothersome symptom of hives, and it may be severe enough to interfere with work and sleep.

Severe pain, blood blister-like spots, and bruising of the skin are not typical of hives. Having hives along with a fever and joint pains is also not typical. These symptoms suggest a different condition called urticarial vasculitis, which requires a different treatment.

Angioedema — In up to one-half of people with hives, a condition called angioedema also develops. Angioedema is similar to hives but occurs in the deeper layers of skin. Hives and angioedema can occur at the same time (figure 1).

Symptoms of angioedema include:

●Puffiness of the face, eyelids, ears, mouth, hands, feet, and genitalia (picture 4)

●Swelling that usually affects one side of the body or affects one side more than the other

●A sensation of fullness or discomfort in the area of the swelling

●Slight redness of the skin, although the skin may also be normal in color

Hives as part of a serious allergic reaction — Hives can also occur as part of a more serious allergic reaction. You should see a doctor or nurse as soon as possible if you develop hives or angioedema suddenly, along with other symptoms such as:

●Trouble breathing

●Tightness in the throat

●Nausea or vomiting

●Cramping abdominal pain

●Passing out

TYPES OF HIVES — Hives are classified based upon how long you have the hives. Hives can be:

●Acute (brief)

●Chronic (longstanding)

●Inducible (triggered by certain types of physical stimulation, such as heat, cold, or sun exposure)

When you first get hives, you cannot tell how long they will last, and so you cannot tell if you have acute or chronic hives.

Although all types of hives look similar, they often have different triggers. Learning what triggers your hives can help you to avoid the trigger.

Acute hives — Most cases of hives are acute and will not last beyond a few days to one week or two. Triggers of acute hives can include the following:

●Infections – Infections can cause hives in some people. In fact, viral infections cause more than 80 percent of all cases of acute hives in children. A variety of viruses can cause hives (even routine cold viruses). The hives seem to appear as the immune system begins to clear the infection, sometimes one week or more after the illness begins. The hives usually persist for one week or two and then disappear.

●Drugs – Many types of drugs can trigger hives, including antibiotics and nonsteroidal antiinflammatory drugs (NSAIDs), such as aspirin, ibuprofen, or naproxen. (See "Patient education: Allergy to penicillin and related antibiotics (Beyond the Basics)".)

Painkillers (eg, codeine and morphine), muscle relaxants used in anesthesia, and intravenous contrast dye used in imaging procedures can also trigger hives.

●Insect stings – Stings from certain insects (bees, wasps, hornets, fire ants) can cause hives around the area of the sting. (See "Patient education: Bee and insect stings (Beyond the Basics)" and "Patient education: Imported fire ants (Beyond the Basics)".)

If you get hives all over your body after an insect sting, this may be a sign of a more serious reaction called anaphylaxis. Anaphylaxis must be treated as soon as possible. (See "Patient education: Anaphylaxis treatment and prevention of recurrences (Beyond the Basics)".)

●Food allergies – Food allergy can cause acute hives in some people. Food-associated hives typically appear within 30 minutes of eating the food. The foods most likely to cause hives in children include milk, eggs, peanuts, other nuts, soy, and wheat. The foods most likely to cause hives in adults include fish, shellfish, peanuts, and other nuts. (See "Patient education: Food allergy symptoms and diagnosis (Beyond the Basics)".)

●Physical contact – Hives can occur after you touch certain substances if you are allergic to them. For example, children who are allergic to dogs may get hives if a dog licks them. Other things that can cause hives (if you are allergic) include plants, raw fruits and vegetables, and latex (found in balloons, latex gloves, condoms, and other common items).

Chronic hives — Chronic hives occur daily or almost daily and last longer than six weeks, sometimes for years. Chronic hives can be frustrating because they come and go and can interfere with sleep, work, or school. Hives affect how you look, and people may worry about being near you for fear that you have a contagious infection.

However, it is important to remember the following:

●Hives are not contagious.

●Chronic hives are rarely permanent; almost 50 percent of people are hive-free within one year.

●Chronic hives are rarely caused by allergies and are not life threatening.

●The bothersome symptoms of chronic hives are treatable in most people.

In most cases of chronic hives, the cause is unknown. Researchers suspect that problems in the immune system play a role.

Hives can be a sign of several other medical or autoimmune conditions, including thyroid or liver diseases, chronic infections, or lupus. Most people with one of these conditions will have other symptoms apart from the hives.

Inducible hives — Hives can be triggered by a variety of physical factors:

●Exposure to cold – The hives often appear as the cold skin warms again.

●Changes in body temperature or sweating – These hives are often tiny and numerous and appear on reddened skin.

●Vibration – Palms may become red, swollen, and itchy after holding onto the steering wheel of a car while driving.

●Pressure – Hives on the palms or the soles of the feet can occur hours after carrying heavy objects or walking long distances. Because the skin on the palms and soles is thick, these areas may appear reddened and swollen without clear hives.

●Exercise – Hives that appear during exercise can be a sign of a dangerous condition called exercise-induced anaphylaxis.

●Sunlight or water – This is rare.

There are also things that do not usually cause hives and swelling but can make them harder to control. These include over-the-counter NSAID medications used to treat pain and fever (such as ibuprofen [sample brand names: Advil, Motrin], naproxen [sample brand names: Aleve, Naprosyn], and aspirin) and any kind of opioid medication. Acetaminophen (sample brand name: Tylenol) does not worsen hives or swelling, so this can be used to treat pain and fever instead. Other factors include alcohol; stress; sleep deprivation; and, for people who menstruate, monthly periods.

Finally, there is a common condition called dermographism (literally "skin writing"). People with this condition develop reddened, raised lines if the skin is stroked firmly or scratched.

Inducible hives tend to be long lasting and are considered a type of chronic hives.

HIVES TESTING — Most people with hives do not need any testing. The diagnosis is usually based on their symptoms and a physical examination. However, tests may be recommended if hives do not resolve within six weeks.

Testing — Skin testing for food and drug sensitivities may be recommended if there are concerns about allergies as a cause of symptoms. This is usually done for people with acute hives. Chronic hives are rarely caused by an allergy. (See "Patient education: Food allergy symptoms and diagnosis (Beyond the Basics)".)

Blood tests are sometimes done if hives continue for six weeks or longer. Blood tests can tell if there are signs of underlying diseases, such as thyroid problems or an autoimmune disease.

Skin biopsy — A skin biopsy (when a small sample of skin is removed) may help identify uncommon causes of hives. A skin biopsy may be recommended for people who have chronic hives along with other symptoms, such as persistent fever, painful hives, individual hives that last for days at a time, or hives associated with bruising of the skin. A skin biopsy may also be recommended for people who have other symptoms or abnormal blood tests.

HIVES TREATMENT — Hives are treated with a combination of avoiding things that cause or worsen the hives, plus the use of medications.

Avoiding triggers — The first treatment for hives is to figure out what is triggering your hives and then avoid that trigger. Even if you cannot figure out the trigger, hives usually disappear over days or weeks.

Antihistamines — Antihistamines are medicines that can relieve itching. Most people with hives respond to antihistamines. You may need a relatively high dose to control your symptoms.

There are different types of antihistamines. They differ in side effects, cost, how long the medicine lasts, and need for a prescription.

●Nonsedating antihistamines – Nonsedating antihistamines are generally preferred for treating hives because they have fewer side effects than older antihistamines. Also, these antihistamines have to be taken less often, usually once or twice per day. Many of them can be purchased over the counter, including:

•Loratadine (sample brand name: Claritin)

•Cetirizine (sample brand name: Zyrtec)

•Fexofenadine (sample brand name: Allegra)

•Levocetirizine (sample brand name: Xyzal)

●Older antihistamines – Older antihistamines start to work quickly and work well to relieve symptoms. Some of these require a prescription, while others can be purchased over the counter. The problem with older antihistamines is that you have to take a dose four to six times per day, and many people have bothersome side effects. These can include drowsiness, dry mouth, double or blurred vision, or difficulty urinating.

Some of these side effects interfere with driving and tasks requiring quick reactions, similar to the effects of drinking alcohol. These medicines are therefore not recommended for people who plan to drive, pilot aircrafts or boats, or operate heavy machinery or for people whose job performance may be otherwise affected. Starting the medicine at a low dose and gradually increasing the dose can help to ease side effects. The side effects usually get better if you take the medicine regularly over a period of days to weeks.

The older antihistamines include:

•Diphenhydramine (sample brand name: Benadryl)

•Chlorpheniramine (sample brand name: Chlor-Trimeton)

•Cyproheptadine (sample brand name: Periactin)

●Other antihistamines – There is another type of antihistamine that is commonly used to treat heartburn. Your doctor or nurse might recommend one of these medicines in combination with another antihistamine if one medicine alone does not work for you. Examples of this type of antihistamine include:

•Famotidine (sample brand name: Pepcid)

•Cimetidine (sample brand name: Tagamet)

●Very sedating antihistamines – There are some very sedating antihistamines that are usually reserved for bedtime use. These can cause significant drowsiness and should not be taken when driving or working. They are sometimes helpful for getting a better night's sleep when itching is severe. Some of these medications require a prescription.

Examples include:

•Hydroxyzine (sample brand names: Atarax, Vistaril)

•Doxepin (sample brand name: Silanor, Sinequan)

Oral steroids — A high dose of antihistamines is usually recommended before trying other treatments. However, oral steroids (glucocorticoids), such as prednisone, can help to relieve severe acute hives that do not get better with antihistamines. Once the hives have improved, the steroid dose is gradually lowered and then stopped.

Oral steroids may be used temporarily to relieve chronic hives, but they should not be used for long-term treatment. This is because steroids can have serious side effects when taken for long periods of time (months or years). If you are taking oral steroids for more than one month per year to control your hives, you should see a specialist (an allergist or a dermatologist).

Other medicines — If your hives do not get better with the treatments discussed above, other treatments are available. One example is montelukast (brand name: Singulair), a medicine that helps with itching and hives in some people when used together with antihistamines. If your hives are not responding to the treatments you have been offered, you should see a specialist (an allergist or a dermatologist). Omalizumab is a treatment for very difficult-to-control hives and is given by specialists. It is given as a monthly injection.

Medication safety during pregnancy — If you are pregnant or planning to try to get pregnant, talk with your health care provider about the medications you take. Some medications are safe to take during pregnancy, while others are not. Your provider can work with you to find a safe way to treat your hives.

WHERE TO GET MORE INFORMATION — Your health care provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed on our website (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for health care professionals, are also available. Some of the most relevant are listed below.

Patient level information — UpToDate offers two types of patient education materials.

The Basics — The Basics patient education pieces 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.

Patient education: Hives (The Basics)
Patient education: Angioedema (The Basics)
Patient education: Primary biliary cholangitis (primary biliary cirrhosis) (The Basics)
Patient education: Chronic hives (The Basics)
Patient education: Inducible hives (The Basics)

Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.

Patient education: Allergy to penicillin and related antibiotics (Beyond the Basics)
Patient education: Bee and insect stings (Beyond the Basics)
Patient education: Imported fire ants (Beyond the Basics)
Patient education: Anaphylaxis treatment and prevention of recurrences (Beyond the Basics)
Patient education: Food allergy symptoms and diagnosis (Beyond the Basics)

Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.

Allergic and asthmatic reactions to food additives
An overview of angioedema: Clinical features, diagnosis, and management
An overview of angioedema: Pathogenesis and causes
Anaphylaxis: Emergency treatment
Approach to the clinical dermatologic diagnosis
Bedbugs
Chigger bites
Chronic spontaneous urticaria: Clinical manifestations, diagnosis, pathogenesis, and natural history
Chronic spontaneous urticaria: Standard management and patient education
Clinical manifestations of food allergy: An overview
Diagnostic evaluation of IgE-mediated food allergy
Differential diagnosis of anaphylaxis in adults and children
Drug eruptions
Overview of cutaneous lupus erythematosus
New-onset urticaria
Urticarial vasculitis
Physical (inducible) forms of urticaria
Cold urticaria
Exercise-induced anaphylaxis: Management and prognosis
Photosensitivity disorders (photodermatoses): Clinical manifestations, diagnosis, and treatment

The following organization also provides reliable health information.

●National Library of Medicine (medlineplus.gov/hives.html)

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