ConditionInfections
Food Allergy
A food allergy is an immune system reaction to a specific food protein. Even a tiny amount can trigger symptoms within minutes to 2 hours: hives, swelling, vomiting, wheezing or, in the most severe cases, anaphylaxis, which can be fatal. Nine foods cause most reactions in the US, including peanuts, tree nuts, milk, eggs, fish, shellfish, wheat, soy and sesame. Treatment is strict avoidance, carrying epinephrine auto-injectors, and in some cases oral immunotherapy.
Also called: Food allergies, IgE-mediated food allergy, food hypersensitivity
At a glance
- What it is
- An immune (usually IgE antibody) reaction to a food protein.
- How common
- About 1 in 13 children and around 1 in 10 adults in the US report a food allergy.
- Top allergens (US)
- Milk, egg, peanut, tree nuts, fish, shellfish, wheat, soy and sesame.
- Symptoms
- Hives, swelling, itching, vomiting, belly pain, wheezing, throat tightness, anaphylaxis.
- Management
- Avoidance, epinephrine auto-injector, written emergency plan; oral immunotherapy for some.
When to get help
Call 911 or go to the ER
- Trouble breathing, wheezing, repeated coughing, throat tightness, hoarse voice or trouble swallowing after eating
- Swelling of the tongue or lips with any breathing difficulty
- Pale, floppy, dizzy or fainting after eating, or symptoms in two body systems (for example hives plus vomiting)
- In all of these: use the epinephrine auto-injector right away, then call 911 or your local emergency number
See a doctor within a day or two
- A first reaction with widespread hives or facial swelling, even if it settled
- Repeated vomiting after a new food in a baby, with pallor or floppiness (possible FPIES)
Book a routine appointment
- Mild itching of the mouth after raw fruit or vegetables (possible oral allergy syndrome)
- Eczema that is hard to control in an infant, to discuss allergy evaluation and early food introduction
- Suspected food allergy that has not been confirmed by testing
Usually safe to manage at home
- A few hives around the mouth after a known allergen with no other symptoms, if your allergist's plan says antihistamines are appropriate, while watching closely for progression
What happens in a food allergy
In IgE-mediated food allergy, the immune system mistakenly produces IgE antibodies against a food protein. These antibodies sit on mast cells in the skin, gut and airways. When the food is eaten again, the protein binds the antibodies and triggers the release of histamine and other chemicals, causing symptoms within minutes to about 2 hours.
Some food allergies are non-IgE-mediated, with delayed symptoms mainly in the gut, such as FPIES (food protein-induced enterocolitis syndrome) and eosinophilic esophagitis.
Common food allergens
| Food | Notes |
|---|---|
| Milk | Most common in infants; most outgrow it. See milk allergy |
| Egg | Common in young children; many outgrow it |
| Peanut | Often lifelong; a leading cause of severe reactions |
| Tree nuts | Cashew, walnut, pistachio, almond and others; usually lifelong |
| Fish | Often begins in adulthood; usually lifelong |
| Shellfish | Shrimp, crab, lobster; the most common adult-onset allergy |
| Wheat | Mostly children; often outgrown |
| Soy | Mostly children; often outgrown |
| Sesame | Added to US major allergen labeling law in 2023 |
Symptoms
- Skin: hives, redness, itching, swelling of lips, eyes or face (angioedema)
- Mouth and throat: itching, tingling, swelling of the tongue, throat tightness, hoarseness
- Gut: nausea, vomiting, belly cramps, diarrhea
- Breathing: sneezing, runny nose, coughing, wheezing, shortness of breath
- Circulation: dizziness, pale skin, weak pulse, fainting
Anaphylaxis
Anaphylaxis is a severe, rapid, whole-body allergic reaction involving breathing problems, a drop in blood pressure, or symptoms in two or more body systems. It can be fatal within minutes. Epinephrine is the first and most important treatment. Antihistamines do not stop anaphylaxis.
Risk factors for severe reactions include asthma (especially poorly controlled), peanut or tree nut allergy, adolescence and delayed epinephrine.
Food allergy vs food intolerance
| Food allergy | Food intolerance | |
|---|---|---|
| Mechanism | Immune system | Digestive (for example, lack of an enzyme) |
| Amount needed | Tiny amounts can trigger it | Usually related to the amount eaten |
| Symptoms | Hives, swelling, vomiting, breathing problems, anaphylaxis | Bloating, gas, diarrhea, discomfort |
| Danger | Can be life-threatening | Uncomfortable but not dangerous |
| Example | Peanut allergy | Lactose intolerance |
Celiac disease is a separate autoimmune reaction to gluten.
Diagnosis
Diagnosis needs an allergist, because tests can be misleading on their own.
- Detailed history: what was eaten, how much, timing and symptoms
- Skin prick testing: a tiny amount of allergen is pricked into the skin; a raised wheal suggests sensitization
- Specific IgE blood tests, including component testing for some foods such as peanut
- Oral food challenge: eating gradually increasing amounts under medical supervision. This is the gold standard
A positive skin or blood test without symptoms (sensitization) does not always mean true allergy. Panel testing for many foods without a history is discouraged, as it leads to unnecessary avoidance. IgG food tests are not valid for diagnosing allergy.
Treatment and management
Avoidance
- read every ingredient label. US law requires the 9 major allergens to be clearly declared
- be aware of cross-contact in kitchens and restaurants
- inform schools, workplaces and restaurant staff
Emergency plan
- carry two epinephrine auto-injectors at all times (or an epinephrine nasal spray where available)
- have a written anaphylaxis action plan
- use epinephrine at the first signs of anaphylaxis, then call 911; a second dose may be given after 5 to 15 minutes if needed
- wear medical ID
Immunotherapy and other treatments
- Oral immunotherapy (OIT): gradually increasing daily amounts of the allergen to raise the reaction threshold. An approved product exists for peanut allergy in children
- Omalizumab: an injected antibody approved to reduce reactions to accidental exposure to multiple foods
- Antihistamines for mild symptoms only
Prevention in infants
The AAP and NIAID recommend introducing peanut-containing foods (in a safe, age-appropriate form such as thinned peanut butter) around 4 to 6 months, after some solids, especially in babies with severe eczema or egg allergy, who may need allergist guidance first. Introducing egg and other allergens early also appears to reduce risk.
Frequently asked questions
What are the symptoms of a food allergy?
Symptoms appear within minutes to 2 hours of eating and include hives, itching, swelling of lips or face, vomiting, belly pain, coughing, wheezing and throat tightness. Severe reactions (anaphylaxis) cause breathing difficulty and a drop in blood pressure.
What is the difference between a food allergy and an intolerance?
A food allergy involves the immune system and can cause life-threatening reactions from tiny amounts. A food intolerance, such as lactose intolerance, is a digestive problem causing bloating, gas or diarrhea, and is not dangerous.
How are food allergies diagnosed?
An allergist combines your history with skin prick tests or blood tests for specific IgE. An oral food challenge under supervision is the most reliable test. Testing without a clear history can give misleading results.
Can food allergies go away?
Many children outgrow milk, egg, wheat and soy allergies. Peanut, tree nut, fish and shellfish allergies usually last for life, though some children outgrow peanut allergy. Your allergist can retest to see whether an allergy has resolved.
Sources
This guide was written from current patient and clinical guidance, including:
- National Institute of Allergy and Infectious Diseases (NIAID): Guidelines for the Diagnosis and Management of Food Allergy in the United States
- American Academy of Allergy, Asthma & Immunology: Food allergy
- US FDA: Food allergies (FASTER Act, major allergens)
- Food Allergy Research & Education (FARE): Food allergy facts
- American Academy of Pediatrics: Early introduction of allergenic foods