Peanut, tree nut, and seed allergy: Management

INTRODUCTION — Peanut, tree nut, and seed allergies are some of the most common food allergies in both children and adults. These allergies tend to cause severe reactions and usually persist over time.

This topic reviews various aspects of management of peanut, tree nut (eg, almond, Brazil nut, cashew, hazelnut, macadamia nut, pecan, pine nut, pistachio, walnut), and seed (eg, sesame, mustard, poppy, flax, sunflower) allergy, including instructions about avoidance of these allergens, education in the proper management of accidental exposures, and monitoring for resolution of the allergy. The epidemiology, pathogenesis, clinical features, and diagnosis of peanut, tree nut, and seed allergy are discussed separately. General discussions of food allergy are presented separately in appropriate topic reviews. (See "Peanut, tree nut, and seed allergy: Clinical features" and "Peanut, tree nut, and seed allergy: Diagnosis".)

The management of food allergy in the specific settings of schools and camps is discussed in detail separately. (See "Food allergy in schools and camps".)

DIETARY RECOMMENDATIONS — Management of peanut, tree nut, and seed allergies begins with instructions about avoidance of products containing these foods.

Avoidance — The most straightforward approach in managing any food allergy is complete avoidance of the culprit food (Food Allergy Research and Education [FARE]). Foods that are at higher risk of containing peanut, tree nuts, or seeds include African, Asian, and Mexican dishes; baked goods (eg, pastries, cookies, crackers, bread); and candy. (See "Management of food allergy: Avoidance" and "Food allergy in children: Prevalence, natural history, and monitoring for resolution", section on 'Role of avoidance'.)

Peanut, tree nuts, and seeds are not essential components of the diet for most people. However, these foods are found in many products. The most straightforward approach in managing any food allergy is complete avoidance of the culprit food and all similar foods. This strategy would be logically expected to minimize the chances of accidental exposure to the culprit food through cross-contact.

However, there may be disadvantages to the strategy of avoiding all similar foods [1]. There is some evidence, for example, that removing foods from the diet can increase the risk of becoming allergic to them [2]. Possible reasons for the heightened sensitivity include both lack of exposure through ingestion and the opposite explanation, namely, ongoing low-level exposure (through hidden sources or cross-contact). In addition, there may be nutritional, social, or cultural reasons that patients may wish to add certain foods to the diet [1,3]. (See "Pathogenesis of food allergy".)

Counseling about avoidance should include discussions about the following issues:

●Cross-contact and hidden ingredients – Patients must be counseled about the potential for accidental exposure to food allergens via cross-contact (ie, inadvertent exposure to the allergenic food by contamination of "safe" foods with small amounts of the culprit food). This can happen anywhere food is served, including restaurants and bakeries. Peanut butter is sometimes used as a thickener in chili and sauces. Seed and legume flours are used in baked goods and pastas. (See "Management of food allergy: Avoidance", section on 'Skills for daily living'.)

●Food labels – Patients must read all food labels (FARE). Legislation was enacted in the United States mandating that the ingredients labels on food packages clearly identify the presence of nine specified allergenic foods, including peanut, tree nuts, sesame, egg, milk, wheat, soybeans, fish, and crustacean shellfish. Labeling legislation has been enacted in other countries as well; however, there are differences in food allergens that are included as well as what food products are covered by these regulations. As an example, regulations in Canada, the European Union, Australia, and the United States include sesame as an allergen, but other countries do not yet include sesame [4,5]. (See "Management of food allergy: Avoidance", section on 'Food labeling'.)

●Precautionary allergen labeling – Some products in the United States and other countries may have precautionary allergen labeling (PAL; also called advisory labeling), such as "may contain peanut." This type of labeling is not regulated, and presence or absence of PAL does not reliably convey actual risk. The most commonly labeled items include chocolate candy, cookies, and baking mixes [6]. We advise patients with peanut, tree nut, and/or seed allergy to avoid all products with PAL for these foods. (See "Management of food allergy: Avoidance", section on 'Advisory labeling' and "Peanut, tree nut, and seed allergy: Clinical features", section on 'Threshold dose'.)

The risk of allergic reactions to these products is not known, but contamination with clinically significant amounts of peanut allergen was found in a small proportion of products with peanut advisory labeling [7]. Some individuals with peanut allergy react to minute amounts of peanut allergen, and these reactions can be severe [8-12]. However, it is rare for patients to know what their threshold dose is for triggering a reaction, and it may vary when the person has a viral infection, participates in aerobic activities, or is taking nonsteroidal antiinflammatory drugs (NSAIDs).

●Tree nuts and lupine in patients with peanut allergy – Approximately one-third of patients with peanut allergy react to tree nuts. Therefore, unless they are ingesting certain tree nuts, it is important to rule out possible tree nut allergies before allowing these patients to ingest tree nuts. We discourage the ingestion of nuts in products from bakeries or restaurants since peanuts are not uncommonly added/substituted for tree nuts. We recommend that children just eat the "allowed" nuts when with their parent(s)/caregiver(s) and continue to avoid peanut and all tree nuts at school/camp to avoid issues with cross-contact, confusion regarding which nuts to avoid, and misidentification.

A high rate of serologic cross-reactivity is seen between peanut and other legumes, including lupine, but reported clinically relevant cross-reactivity is low. Up to 44 percent of patients with peanut allergy are sensitized to lupine, but clinical reactivity ranges from 4 to 28 percent [13].

●Medications – Some medications, such as a few metered-dose inhalers and propofol, contain soy lecithin. Soy lecithin is derived from highly processed soy oil and has very little, if any, soy protein. It can be consumed safely by nearly all patients with soy allergy. Thus, these medications are unlikely to be unsafe in patients with peanut allergy, and, therefore, we do not tell patients with peanut allergy to avoid these medications. (See "Management of food allergy: Avoidance", section on 'Food allergens in nonfood items'.)

●Other nonfood sources – Skin preparations and hair products may have ingredients derived from peanut, tree nuts, or seeds. Allergen exposure through skin contact may cause localized reactions but is unlikely to trigger severe systemic allergic reactions [14]. The Food Allergen Labeling and Consumer Protection Act of 2004 only applies to the labeling of foods regulated by the US Food and Drug Administration (FDA); therefore, skin care and hair products are not covered by this legislation. (See "Management of food allergy: Avoidance", section on 'Food allergens in nonfood items'.)

Clinical scenarios — The clinician's recommendations must carefully balance the patient's preferences with what is known about cross-reactivity among these foods if a patient with an allergy to peanut or a certain tree nut or seed wishes to continue eating other forms of nuts or seeds. The severity of the patient's reaction, age of the patient, and nutritional needs also influence the decision. (See "Food allergens: Clinical aspects of cross-reactivity" and "Peanut, tree nut, and seed allergy: Clinical features", section on 'Allergies to other foods'.)

The following scenarios illustrate some of the issues involved and our management approach. Individual clinicians may decide to adopt different strategies depending upon their level of expertise and the resources available (eg, ability to perform oral food challenges).

●For patients who have experienced life-threatening anaphylaxis to peanut or a specific tree nut or seed, we recommend avoidance of that specific food and also suggest avoidance of all common clinically cross-reactive foods. Peanut and tree nuts are often processed in the same facilities, and therefore there is a risk of accidental exposure due to cross-contact. Furthermore, young patients with an allergy to peanut are at high risk for developing an allergy to tree nuts. (See "Peanut, tree nut, and seed allergy: Clinical features", section on 'Allergies to other foods'.)

Specifically, we recommend that patients with severe peanut allergy avoid tree nuts and cross-reactive legumes until an evaluation is performed and it is clearly determined that they can tolerate these foods. Certain legumes are more allergenic or have higher rates of cross-reactivity with peanut; these include green pea, chickpea, and lentil [13]. In younger children with severe peanut allergy, one option is to advise avoidance of lupine and all tree nuts, in addition to peanut, even if testing is negative. In older children and adults, we allow them to eat tree nuts and lupine if they wish and if we have determined that they are not reactive (ie, a negative test is sufficient if there is no reaction history; otherwise, we perform a food challenge to confirm lack of reactivity) [15]. We counsel these patients about the potential increased risk of cross-contact with this approach.

We suggest avoidance of all tree nuts for patients with a severe tree nut allergy. These patients may continue to eat peanut and/or specific tree nuts if they are already in their diet. If peanut is not already in their diet, it may be introduced if testing is negative. We counsel them about the precautions discussed above if they choose to eat peanut and/or specific tree nuts.

●We are more flexible in our approach for patients with non-life-threatening reactions to peanut, tree nuts, and/or seeds. We do not discourage patients from avoiding peanut and all tree nuts if that is what they prefer to do. However, a careful evaluation must be performed to determine which cross-reacting foods that a patient has not eaten in the past may be safely consumed if a patient wishes to include some of these foods in their diet.

As an example, a patient who develops an allergy to a tree nut that is moderate in severity and has been avoiding peanut and all tree nuts may ask about the safety of eating peanut, which had not been a regular component of the patient's diet before the reaction. In this case, we would first perform skin testing with a commercial peanut extract. If negative, we would allow the ingestion of peanut because the experience at the author's institution suggests the negative predictive value of skin prick testing (SPT) for peanut is generally high. If the skin test was positive to peanut, we would evaluate the level of peanut-specific immunoglobulin E (IgE) in the blood. If the level was <15 kU_A/L and the patient had an interest in eating peanut, we would perform a food challenge to determine whether there was true clinical reactivity (because false-positive skin tests are not uncommon, and patients may have low levels of allergen-specific IgE without developing clinical symptoms). An oral food challenge with peanut would also be performed if there was any clinical suspicion of peanut allergy or if the clinician was uncomfortable proceeding without additional evaluation. The same process can be undertaken if a patient has an interest in including specific tree nuts in the diet.

It is typically easier to liberalize the diet to allow peanut, compared with allowing some tree nuts, in people with a tree nut allergy. One can purchase commercial-grade peanut butter that is not contaminated with tree nuts, but it is more complicated to find tree nut-containing products without cross-contact risks. An increasing number of commercial food products are processed in single-nut facilities, enabling the safe inclusion of selected nuts in the diet. Nuts in the shell are another way of eating selected nuts in a safe manner. Label reading continues to be an integral part of allergy management, and patients should be reminded to check every package as labels may change over time.

●We allow people to continue to eat nuts or seeds that have not caused symptoms in the recent past and which they have eaten regularly (similar to having just passed an oral food challenge) if they wish to do so. As an example, a patient with a newly diagnosed allergy to cashew who continued to eat peanut and almond without incident after the reaction to cashew can continue to eat peanut, other tree nuts (except pistachio, in this case, since cross-reactivity is higher), and seeds. We discuss with the patient that by keeping peanut and almond in the diet, there is some increased risk of accidental exposure to cashew due to cross-contact. In addition, we discuss the rare possibility of developing additional tree nut allergies over time if the patient is a young child.

●Patients sometimes present with a positive test to a food, such as peanut, that they are currently eating on a regular basis. We do not advise removal of the food from the diet in this case. However, we do discuss with the patient that, on rare occasions, individuals may convert from sensitization to clinical reactivity. In most cases in which this occurs, peanut has been removed from the diet because of a "positive" test result despite no history of clinical reactivity, and clinical symptoms develop when peanut is reintroduced into the diet [16].

●Another common scenario is the patient who was tested for food allergies because of a history of other food allergies, atopic disease, or family history and tested positive to a food such as peanut but has never ingested the food. In two studies, one-half of a group of atopic, peanut-naïve children who had a skin test reaction to peanut of ≥3 mm or peanut-specific IgE ≥0.35 kU_A/L reacted to peanut when challenged [17,18]. In this situation, we take into consideration the size of the SPT reaction and/or the level of specific IgE, the age of the patient, and the preferences of the patient and parent(s)/caregiver(s). (See "Peanut, tree nut, and seed allergy: Diagnosis".)

●We generally do not restrict other legumes from the diet in patients with peanut allergy, except for lupine since it appears to have greater clinical cross-reactivity with peanut. Most children have already eaten and tolerated various legumes (eg, soy, pea, string bean, etc) prior to their initial peanut reaction. We typically advise patients that they may continue to eat the tolerated legumes and introduce others into the diet without additional testing. Of note, there is a high rate of false-positive tests to legumes in patients with peanut allergy, making screening tests unreliable. However, we will often test patients who are highly allergic to peanut to other legumes that have greater clinical cross-reactivity with peanut (eg, chickpea and lentil) by performing skin tests and sometimes serum IgE tests if they have not already shown tolerance to at least several legumes or if there are concerns of reactions to some legumes. Introduction of additional legumes may require clinician-supervised oral food challenges, depending upon these results and the degree of clinical concern.

MANAGEMENT OF ACUTE IgE-MEDIATED REACTIONS — Identification of individuals with IgE-mediated allergy is important because these patients are at risk for severe reactions. The majority of allergic reactions to peanut, tree nuts, or seeds are systemic. These foods are also among the more common causes of food-induced anaphylaxis, particularly fatal and near-fatal anaphylaxis. (See "Food-induced anaphylaxis" and "Fatal anaphylaxis" and "Peanut, tree nut, and seed allergy: Clinical features", section on 'Types of reactions'.)

The severity of symptoms in a given individual with peanut, tree nut, or seed allergy may vary considerably between reactions. In addition, the severity of an initial reaction does not predict the severity of subsequent reactions. (See "Peanut, tree nut, and seed allergy: Diagnosis".)

As examples:

●Members of a United States-based registry of individuals with peanut and/or tree nut allergy reported that subsequent reactions due to accidental ingestion were commonly more severe than their initial reactions [19].

●An Australian study of peanut allergy found that 30 percent of patients who had experienced anaphylaxis had preceding milder reactions.

●In a small study of children with peanut allergy in Singapore, one-half of those who had an accidental exposure had a reaction of greater severity than their initial reaction [20].

●Children whose only apparent clinical manifestation of food allergy is atopic dermatitis are at risk of an acute systemic reaction upon reintroduction of that food after an elimination diet [21-23].

Furthermore, skin test and specific IgE results are not predictive of the severity of reactivity to a food. Accordingly, we suggest that individuals diagnosed with IgE-mediated peanut, tree nut, or seed allergy have an epinephrine autoinjector(s) available at all times [24]. In addition, the patient should have a written anaphylaxis emergency action plan (Anaphylaxis Emergency Action Plan - English) (Anaphylaxis Emergency Action Plan - Spanish). These measures are discussed in detail separately. (See "Anaphylaxis: Emergency treatment".)

MONITORING FOR RESOLUTION AND REINTRODUCTION — Children with peanut, tree nut, and/or seed allergies should be monitored for resolution ("outgrowing") of the allergy, although it is uncommon to outgrow these allergies after six years of age. The general steps to take to determine if an allergy has resolved are covered in detail separately. The approach for peanut, tree nut, and seed allergies is reviewed here. (See "Peanut, tree nut, and seed allergy: Clinical features", section on 'Natural history and prognosis' and "Food allergy in children: Prevalence, natural history, and monitoring for resolution".)

We perform testing yearly initially (this includes peanut component testing for children with peanut allergy) (see "Component testing for pollen-related, plant-derived food allergies", section on 'Peanut'). Patients who have not had any reactions in the past one to two years and who have tree nut- or peanut-IgE level ≤2 kUA/L and/or tree nut- or peanut- or sesame-skin prick test (SPT) <8 mm are offered a supervised challenge. There are no studies on predictive SPT or IgE values for other seeds or coconut. In addition, there are little data on the utility of peanut component-specific IgE (ie, to Ara h2) in determining whether a peanut allergy has resolved [25]. However, in our clinical experience, patients rarely pass a peanut challenge if the Ara h 2 level exceeds 2.0 kU/L. Thus, we typically wait until the level is less than 1.0 kU/L to offer a peanut challenge. A negative test is not a guarantee that the allergy has resolved, and challenge is necessary to make this determination. As with cow's milk and hen's egg allergy, we also take into account the trend in specific IgE or SPT and the reaction history. As an example, we would generally not offer a food challenge to a child who failed a food challenge with significant symptoms two years ago and has a specific IgE level that has not fallen since then.

The optimal amount of nut/seed that patients should eat and the frequency of ingestion after a successful challenge are unknown. If the challenge is negative, we advise the patient to ingest a normal serving size (eg, the amount in a peanut butter sandwich or nut-containing candy bar) at least once a week. Patients should be followed for at least another year to assure that there are no recurrent symptoms. (See "Food allergy in children: Prevalence, natural history, and monitoring for resolution", section on 'Recurrence'.)

In patients with persistent allergy (eg, they have had an accidental exposure with a reaction) or in whom the specific IgE or SPT remains elevated and unchanged for several years (>50 kU/L or >8 mm SPT), testing can be performed less frequently over time. (See "Food allergy in children: Prevalence, natural history, and monitoring for resolution", section on 'Resolution' and "Food allergy in children: Prevalence, natural history, and monitoring for resolution", section on 'Prognostic factors'.)

RECURRENCE — Peanut allergy rarely may recur in patients who have passed an oral food challenge [2,26-29]. The first cases of reported recurrence occurred in children who did not incorporate peanut into the regular diet after passing the challenge, although it is not clear whether these children refused to eat peanut because they were experiencing some discomfort [2,26]. In addition, subsequent cases have been reported in patients who regularly consumed peanut [27,28].

We advise eating normal serving sizes of the food on a regular basis after passing a food challenge. We also advise patients to maintain an emergency plan for at least one year, until they have proven that the food is tolerated in the regular diet in typical quantities. (See "Oral food challenges for diagnosis and management of food allergies".)

MANAGEMENT OF YOUNGER SIBLINGS — Initial data from observational studies suggested that younger siblings of a child with peanut allergy were at increased risk of developing an allergy to peanut compared with the general population, but subsequent studies indicate that this risk is due in part to delayed introduction [30]. Other risk factors, such as moderate-to-severe eczema, may also play a role. The approach to the introduction of peanut is the same for these infants and children as it is in the general population. This approach is reviewed in greater detail separately. (See "Peanut, tree nut, and seed allergy: Clinical features", section on 'Familial factors' and "Introducing highly allergenic foods to infants and children", section on 'Introduction in higher-risk populations' and "Introducing highly allergenic foods to infants and children", section on 'Suggested approach'.)

ORAL IMMUNOTHERAPY AND OTHER TREATMENTS — Oral immunotherapy is available for peanut and is performed for other foods. Several other treatment strategies with the goal of increasing the threshold of reactivity or even possibly curing or providing long-term remission from food allergy are under investigation. These approaches are either allergen specific or aimed at modulating the overall allergic response. A specific formulation of peanut allergen oral immunotherapy powder was approved by the US Food and Drug Administration (FDA) in 2020 with provision of ongoing monitoring through a Risk Evaluation and Mitigation Strategy (REMS) that includes requirements to assure safe use and minimize risk of anaphylaxis. Oral immunotherapy (OIT) and other investigational therapies are discussed in greater detail separately. (See "Oral immunotherapy for food allergy" and "Experimental therapies for food allergy: Immunotherapy and nonspecific therapies".)

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: Food allergy".)

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 5^th to 6^th 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 10^th to 12^th 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: Peanut, tree nut, and seed allergy (The Basics)")

●Beyond the Basics topics (see "Patient education: Food allergy symptoms and diagnosis (Beyond the Basics)" and "Patient education: Food allergen avoidance (Beyond the Basics)")

SUMMARY AND RECOMMENDATIONS

●Avoidance – Management of peanut, tree nut, and seed allergies includes instructions about avoidance of products containing these foods and determination of which similar foods may be ingested safely (Food Allergy Research and Education [FARE]). The most straightforward approach in managing any food allergy is complete avoidance of the culprit food and all similar foods. This includes eating food from Asian (including Chinese and Thai) and Mexican restaurants, bakeries, and ice cream parlors because peanut, tree nuts, and sesame are commonly used in these types of establishments. However, there are disadvantages to this strategy. Thus, the clinician's recommendations must carefully balance the patient's preferences with what is known about cross-reactivity among foods. The severity of the patient's reaction, age of the patient, and nutritional needs also influence the decision. (See 'Dietary recommendations' above and "Management of food allergy: Avoidance".)

●Management of accidental exposures – Patients should be educated in the proper management of accidental exposures (Anaphylaxis Emergency Action Plan - English) (Anaphylaxis Emergency Action Plan - Spanish). We prescribe epinephrine autoinjectors for all patients with a history of systemic reactions to peanut, tree nuts, or seeds. We also suggest prescribing epinephrine autoinjectors for all patients with milder immunoglobulin E (IgE) mediated reactions to peanut, tree nuts, or seeds, especially if they have concomitant asthma, given the unpredictable nature of these food allergies (Grade 2B). (See 'Management of acute IgE-mediated reactions' above and "Management and prognosis of oral allergy syndrome (pollen-food allergy syndrome)", section on 'Overview of management'.)

●Monitoring for resolution – Children should be periodically monitored for resolution of their food allergies, although it is very uncommon to outgrow allergy to peanut, tree nuts, and seeds beyond six years of age. A supervised oral food challenge should be performed to confirm resolution of the allergy. (See 'Monitoring for resolution and reintroduction' above and "Peanut, tree nut, and seed allergy: Clinical features", section on 'Natural history and prognosis' and "Food allergy in children: Prevalence, natural history, and monitoring for resolution".)

●Recurrence after reintroduction – Recurrence of peanut allergy rarely may occur after a patient has passed an oral food challenge. (See 'Recurrence' above.)

●Oral immunotherapy and investigational therapies – Several treatments are under investigation that may temporarily "desensitize" or provide long-term remission from food allergy. (See 'Oral immunotherapy and other treatments' above and "Experimental therapies for food allergy: Immunotherapy and nonspecific therapies" and "Oral immunotherapy for food allergy".)

ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Hugh A Sampson, MD, who contributed to earlier versions of this topic review.