In the United States, approximately 2% to 3% of adults and 8% of children have a food allergy, and 40% of those children have multiple food allergies.^1,2 About 40% of food allergies in children are reported as severe, which can lead to significant costs and anxiety for parents and caregivers.² Common foods that produce allergies are peanuts, cow's milk, shellfish, tree nuts, egg, fish, soy, and wheat.^2,3 Peanut allergy, the most common (2%), is the leading cause of life-threatening anaphylaxis.^2,4 Children are likely to outgrow allergies to egg, cow's milk, wheat, and soy, whereas peanut, tree nut, fish, and shellfish allergies tend to persist throughout life.³ Peanut allergy resolves in approximately 1 in 5 children in the first four years of life.⁵

Risk Factors

Children with asthma, allergic rhinitis, atopic dermatitis, or an allergy to insect venom, medications, or latex are at an increased risk of developing food allergies^2,6 (Table 1²). Children with vitamin D insufficiency, a history of antibiotic use in the first two years of life, or a family history of atopy also have an increased risk of developing food allergies.^3,7,8 Other factors, including exercise, emotional stress, menses, alcohol consumption, and having a viral infection, can lower the reaction threshold and increase the risk of having an allergic reaction to food.^4,6

Symptoms

Food allergies are classified as immunoglobulin E (IgE)- and non–IgE-mediated. IgE-mediated allergies typically have a rapid onset, within seconds to minutes (e.g., pruritus, anaphylaxis). Non–IgE-mediated food allergies are characterized by delayed reactions, within hours to several days (e.g., food protein allergy–induced colitis).^6,9,10 The severity of the reaction is influenced by the amount of food ingested, form of the food (i.e., how it was prepared), and presence of other ingested foods.⁶ Symptoms of food allergies are listed in Table 2.^3,6,9,11

Diagnosis

The rates of food allergies are overestimated because of self-reported food allergies that may be food intolerances.^1,12 Food intolerances are adverse reactions without an immunologic cause (e.g., lactose intolerance) and can be mistaken for food allergies.⁶ Differential diagnosis of food allergies is included in Table 3.^1,6

Diagnosis starts with a detailed history from the parent, caregiver, or patient. The amount and type of food that was eaten, form of the food (e.g., raw, extensively baked), time from ingestion to symptoms, presence of symptoms not associated with food, presence of risk factors that increase the likelihood of an allergic reaction (e.g., exercise), and number of reactions are essential components of an allergy-focused history.^6,9,10,12 Non–IgE-mediated food allergies should be considered in children without an adequate response to treatment for atopic dermatitis, gastroesophageal reflux disease, and chronic gastrointestinal symptoms, including chronic constipation.⁹

Serum IgE or skin prick testing (SPT) should be performed only in patients whose allergy-focused history indicates a high pretest probability of a food allergy. Doing so promptly can prevent unnecessary food avoidance and strain for patients and their families.^3,9,12

SPT should be performed only in facilities equipped to handle anaphylactic reactions and interpreted by clinicians with an adequate knowledge of history, clinical findings, and allergen pathology.⁹ SPT can be performed on patients of any age and has high sensitivity and high negative predictive values.^1,6 Children younger than two years and adults older than 70 years may have smaller positive results.¹ The likelihood of allergy reactivity can be estimated with correlation of wheal size.^3,10

SPT has greater sensitivity than serum IgE testing.¹ Drawbacks of SPT include the lack of standardization of the extracts used and the interference of antihistamine and certain antidepressant medications.^6,10 Before SPT, patients should abstain from the use of high-potency topical steroids on test sites for three weeks and discontinue any antihistamines and antidepressants with antihistamine properties (e.g., tricyclic antidepressants) for one week.¹ It is not necessary to stop leukotriene receptor antagonists, which are often used in the treatment of asthma.¹

Serum IgE testing is preferable to SPT in patients at high risk of anaphylaxis.¹ Patients who cannot tolerate the SPT procedure, have uncontrolled medical conditions (e.g., uncontrolled asthma), take essential medications (e.g., beta blockers for coronary artery disease), or have skin conditions that could interfere with SPT should instead undergo serum IgE testing.¹

Widely available serum IgE tests provide reliable measures with standardization of accurate laboratory techniques and specified 95% positive predictive values of reactivity within a population.^1,6 Serum IgE testing can indicate sensitization to a specific allergen. Care is necessary when interpreting serum IgE results. A positive test result does not necessarily indicate the existence of a food allergy, and the level of specific IgE does not correlate to symptom severity.^1,10 A negative test result may indicate that a patient has not been sensitized (i.e., exposed) to the allergen, leading to an incorrect dismissal of a food allergy.¹

Less commonly used allergy testing is typically done by an allergist and includes intradermal tests, atopy patch tests, and basophil activation tests.¹ Intradermal testing can be performed after a negative result on SPT when the clinician still has a strong suspicion of allergy. However, there is a greater risk of systemic allergic reactions during testing without increased sensitivity over SPT.^1,6 Atopy patch testing is indicated for cell-mediated hypersensitivity reactions, such as medication or latex allergies.¹ Use of basophil activation testing is limited as an unproven and nonstandardized test for diagnosis of food allergy.^1,6

The preferred method of food allergy diagnosis is a double-blind oral food challenge.^11,12 An oral food challenge can reliably disprove a previously diagnosed nonsevere food allergy or confirm an already diagnosed food allergy. It should be done under physician supervision and in a setting capable of managing severe reactions.^10,12 If a child has severe allergic symptoms after a known ingestion and an oral food challenge is not feasible, having no further symptoms after elimination of the food is sufficient for diagnosis.¹¹

Treatment and Management

ELIMINATION DIET

The primary treatment for a food allergy is elimination of the offending food from the diet.¹¹ Nutrition counseling and regular growth monitoring are warranted when multiple foods are eliminated.¹¹ The National Institute of Allergy and Infectious Diseases recommends that families and caregivers receive training on how to understand ingredient lists on food labels.⁶ The U.S. Food Allergen Labeling and Consumer Protection Act of 2004 requires food labels to list when any of the nine major food allergens (i.e., milk, egg, peanuts, tree nuts, soy, wheat, fish, crustacean shellfish, and sesame) are present as ingredients in prepared foods.^6,13 However, including warning labels such as “may contain trace amounts of nuts” or “may be prepared in a facility that also uses nuts” is voluntary.⁶

ALLERGY IMMUNOTHERAPY

No medications are effective for preventing IgE- or non–IgE-mediated allergic reactions to food.¹¹ Oral and sublingual immunotherapies are methods of desensitization therapy. These treatments induce tolerance to an allergenic food by gradually increasing the dose of the allergenic extract.³ Patients receiving oral immunotherapy for peanut, egg, and milk allergies are more tolerant of the allergenic food in oral food challenges than patients receiving placebo.³ Local gastrointestinal and systemic reactions requiring epinephrine have been reported with oral immunotherapy.³ Patients are more likely to achieve clinical desensitization with oral immunotherapy, but there is a higher risk of adverse effects.⁴ Peanut desensitization therapy increases the risk of anaphylactic reactions compared with placebo or avoidance.¹⁴ Immunotherapy (oral and sublingual) with cross-reacting allergens is not recommended to treat food allergies.¹¹

MEDICATIONS FOR ANAPHYLAXIS MANAGEMENT

Epinephrine is the initial drug of choice for the management of food-induced anaphylaxis.⁴ Epinephrine has a short half-life (minutes) and often requires a second dose for treatment of persistent or recurrent symptoms.⁴ Anti-histamines, glucocorticoids, and inhaled beta₂ agonists can be useful for reducing symptoms but should not be used as first-line treatment for anaphylaxis⁴ (Table 4⁶). Epinephrine is available as autoinjectors in three doses. Patients and parents should be instructed on the use and administration of epinephrine and need for further evaluation in the emergency department because hospitalization may be required.⁴

Prevention

Although exclusive breastfeeding for three to four months reduces the likelihood of the child developing eczema and asthma, it has not been shown to reduce the development of food allergies.^6,15 Evidence does not support restricting a mother's diet during pregnancy or while breastfeeding to reduce the risk of food allergies.^6,15,16 Restricting cow's milk supplementation for the first three days of life is associated with a significantly lower risk of developing cow's milk, egg, and wheat allergies by 24 months of age in infants who have an increased risk of atopy.¹⁷ Evidence indicates that infants with early sequential exposure to allergenic foods (peanuts, cow's milk, wheat, and cooked eggs) between four and six months of age are less likely (number needed to treat = 63) to develop food allergies at 36 months than unexposed infants.^16–18 The timing of gluten introduction is not associated with the development of celiac disease, type 1 diabetes mellitus, or any other autoimmune disease.¹⁹

Guidelines for the prevention of peanut allergies recommend that infants with severe eczema, egg allergy, or both be introduced to age-appropriate, peanut-containing food as early as four to six months of age.^12,15,19,20 Other solid foods should be introduced before peanut-containing foods to confirm that the infant is developmentally ready.^15,19 Infants with mild to moderate eczema should start ingesting age-appropriate, peanut-containing food around six months of age¹⁹ (eTable A). In infants without eczema or any food allergy, age-appropriate peanut-containing foods may be introduced with other solid foods in accordance with family preferences and cultural practices.^18–20

Immunizations for Patients With Egg Allergy

Patients with egg allergy, even those with a history of severe reactions, can safely receive vaccines for measles, mumps, rubella, and varicella.⁶ However, vaccines for rabies and yellow fever should not be given to patients with a history of urticaria (hives), angioedema, allergic asthma, or systemic anaphylaxis to egg protein unless an allergy evaluation is performed.⁶ For influenza vaccines, health care professionals should follow current vaccine recommendations from the Advisory Committee on Immunization Practices.¹¹ Most available influenza vaccines, with the exceptions of the quadrivalent recombinant influenza vaccine (RIV4; Flublok) and cell culture–based quadrivalent inactivated influenza vaccine (ccIIV4; Flucelvax), are prepared by propagation of the virus in embryonated eggs and might contain trace amounts of egg proteins, such as ovalbumin.²¹

People with egg allergies can safely receive an influenza vaccine if the reaction is limited to urticaria.²¹ Individuals who report reactions to egg other than urticaria (e.g., angioedema or swelling, respiratory distress, lightheadedness, recurrent vomiting) or require the use of epinephrine or other emergency medical interventions can also receive any licensed, recommended influenza vaccine.²¹ However, if a vaccine other than ccIIV4 or RIV4 is used, administration should occur in an inpatient or outpatient medical setting (e.g., hospitals, clinics, health departments, physician offices) and be supervised by a physician capable of recognizing and managing severe allergic reactions.^21,22

Prognosis

Most children with food allergies will eventually tolerate cow's milk, egg, soy, and wheat. However, tree nut, shellfish, and peanut allergies are more likely to be lifelong.⁶ Most children (75%) with egg and cow's milk allergies can often tolerate baked forms of these foods.³ The time course of food allergy resolution in children varies by food and may occur as late as their teenage years.⁶ An initial high level of allergen-specific IgE against a food is associated with a lower rate of resolution of the allergy over time.⁶

This article updates previous articles on this topic by Yawn and Fenton,¹¹ Kurowski and Boxer,²³ and Sicherer.²⁴

Data Sources: A PubMed search was completed with clinical queries using the key terms food allergies with and without the terms diagnosis, treatment, and prevention. The search included meta-analyses, randomized controlled trials, clinical trials, and reviews. The Cochrane database and Essential Evidence Plus were also searched. Several studies regarding prevalence of food allergies included demographics of race and/or gender as patient categories and were included in our final review. No studies indicated race and/or gender as variables for delineation of diagnosis, treatment, or prevention. Search dates: August 15, 2022, and May 8, 2023.