ConditionWhole body & general
Food Allergies
Food allergies are immune reactions to proteins in specific foods. In the most common type, IgE antibodies trigger symptoms within minutes to 2 hours of eating the food: hives, lip or face swelling, vomiting, wheezing or a life-threatening reaction called anaphylaxis. Nine foods cause most reactions, including peanut, tree nuts, milk, egg, shellfish and fish. Treatment is strict avoidance, carrying epinephrine, and in some cases oral immunotherapy or omalizumab. Food intolerance is different and not dangerous.
Also called: Food allergy, IgE-mediated food allergy, food hypersensitivity, peanut allergy, tree nut allergy, shellfish allergy
At a glance
- What it is
- An immune reaction to a food protein.
- Top allergens (US)
- Milk, egg, peanut, tree nuts, wheat, soy, fish, shellfish, sesame.
- Typical reaction
- Hives, swelling, itching, vomiting, cough, wheeze, within minutes to 2 hours.
- Most dangerous
- Anaphylaxis, which needs epinephrine immediately.
- Management
- Avoidance, label reading, epinephrine auto-injectors, action plan; oral immunotherapy or omalizumab for some.
When to get help
Call 911 or go to the ER
- Trouble breathing, wheezing, throat tightness, hoarse voice, difficulty swallowing, or swelling of the tongue. Use an epinephrine auto-injector immediately and call 911 or your local emergency number
- Dizziness, fainting, pale or blue skin, or a weak pulse after eating
- Repeated vomiting with hives or swelling, or symptoms in two body systems at once (such as hives plus vomiting)
- A child who becomes floppy, very sleepy or pale after eating a known allergen
See a doctor within a day or two
- Hives or lip swelling after eating, even if they settle, if this is the first reaction
- Repeated vomiting 1 to 4 hours after a food in an infant, with pallor or lethargy (possible FPIES)
Book a routine appointment
- Repeated mild itching of the mouth with raw fruit or vegetables (possible oral allergy syndrome)
- Eczema in an infant, to discuss early introduction of peanut and egg
- Planning for school, travel or dining out with a known allergy
What happens in a food allergy
In an IgE-mediated food allergy, the immune system mistakenly identifies a food protein as a threat and makes IgE antibodies against it. These antibodies sit on mast cells in the skin, gut and airways. When the food is eaten again, the protein binds the IgE and mast cells release histamine and other chemicals within minutes, causing symptoms.
Other immune food reactions are not IgE-mediated:
- FPIES (food protein-induced enterocolitis syndrome): delayed repeated vomiting in infants
- Eosinophilic esophagitis: chronic inflammation of the esophagus causing swallowing problems
- Food protein-induced proctocolitis: blood-streaked stools in breastfed or formula-fed babies
Common food allergens
In the US, nine major allergens must be listed on food labels:
| Food | Typical pattern |
|---|---|
| Milk | Most common in infants; most children outgrow it. See milk allergy |
| Egg | Common in young children; many outgrow it |
| Peanut | Usually lifelong; most common cause of fatal reactions with tree nuts |
| Tree nuts | Almond, cashew, walnut, pecan, pistachio, hazelnut; usually lifelong |
| Wheat | Often outgrown; different from celiac disease. See wheat allergy |
| Soy | Common in infants; often outgrown |
| Fish | Often starts in adulthood; usually lifelong |
| Shellfish | Shrimp, crab, lobster; the most common adult food allergy; usually lifelong |
| Sesame | Added to US labeling law in 2023 |
About 8% of children and 10% of adults in the US are estimated to have a food allergy.
Symptoms
Symptoms usually start within minutes and almost always within 2 hours:
- Skin: hives, itching, redness, swelling of the lips, face or eyes
- Mouth and throat: itching, tingling, tongue swelling, throat tightness, hoarseness
- Gut: nausea, vomiting, cramping, diarrhea
- Breathing: cough, wheeze, shortness of breath, nasal congestion
- Circulation: dizziness, fainting, fast heartbeat, low blood pressure
Anaphylaxis
Anaphylaxis is a severe, rapid reaction involving more than one body system, or low blood pressure or breathing difficulty. It can be fatal within minutes. Hives are absent in some cases. Risk is higher in teenagers and young adults, people with asthma, and those with peanut, tree nut or shellfish allergy.
Food allergy vs food intolerance
| Food allergy | Food intolerance | |
|---|---|---|
| Mechanism | Immune system | Digestive (for example, lactase enzyme deficiency) |
| Amount needed | Tiny traces can trigger | Usually dose-dependent |
| Symptoms | Hives, swelling, breathing problems, anaphylaxis | Bloating, gas, diarrhea, discomfort |
| Danger | Can be life-threatening | Uncomfortable, not dangerous |
| Example | Peanut allergy | Lactose intolerance |
Celiac disease is an autoimmune reaction to gluten that damages the small intestine. It is not an allergy and does not cause anaphylaxis, but requires lifelong strict gluten avoidance.
Risk factors
- family history of allergies
- eczema in infancy, especially severe early eczema; allergens may enter through broken skin
- other allergic conditions such as asthma and hay fever
- delayed introduction of allergenic foods in infancy
Diagnosis
An allergist starts with a detailed history: what was eaten, how much, how quickly symptoms started, what they were, and how they were treated.
- Skin prick test: a drop of food extract is pricked into the skin; a raised wheal after 15 minutes suggests sensitization.
- Blood test (specific IgE): measures IgE to the food or its component proteins (component testing helps predict severity for peanut and others).
- Oral food challenge: eating gradually increasing amounts under medical supervision. The gold standard to confirm or rule out allergy.
A positive test alone does not prove allergy; many people are "sensitized" but can eat the food. Avoid broad panels of food tests without a history of reactions, and avoid unproven tests such as IgG panels, hair analysis and kinesiology.
Treatment and management
Avoidance
- Read every label, every time. Watch for "may contain" statements, which are voluntary in the US.
- Tell restaurant staff clearly about your allergy and ask about ingredients and cross-contact.
- Wash hands and surfaces; cross-contact can occur with shared utensils and fryers.
Emergency treatment
- Epinephrine is the first-line treatment for anaphylaxis. Carry two auto-injectors (or epinephrine nasal spray) at all times.
- Inject into the outer thigh at the first signs of a serious reaction, then call 911. A second dose may be needed after 5 to 15 minutes.
- Antihistamines can ease mild skin symptoms but do not stop anaphylaxis.
- Have a written food allergy action plan for home, school and caregivers.
Treatments that raise the threshold
- Oral immunotherapy (OIT): daily, gradually increasing doses of the allergen under specialist supervision. Peanut OIT (Palforzia) is FDA-approved for children. It reduces the risk of reactions to accidental exposure but requires ongoing daily dosing.
- Omalizumab (Xolair): an injection approved in 2024 to reduce allergic reactions to multiple foods after accidental exposure.
- Epicutaneous (skin patch) and other immunotherapies are under study.
Prevention in infants
US guidelines recommend introducing peanut-containing foods around 4 to 6 months for infants at high risk (severe eczema or egg allergy), after consulting a doctor, and around 6 months for others. Early introduction of egg is also recommended. Introducing allergenic foods early and keeping them in the diet regularly reduces the risk of developing allergy. Treating eczema well may also help.
Outlook
Milk, egg, wheat and soy allergies are often outgrown in childhood. Peanut, tree nut, fish and shellfish allergies usually persist. Allergists repeat testing periodically to see whether a child has outgrown an allergy.
Frequently asked questions
What are the symptoms of a food allergy?
Symptoms usually appear within minutes to 2 hours and include hives, itching, swelling of the lips or face, vomiting, stomach cramps, cough, wheezing, or dizziness. Severe reactions (anaphylaxis) involve breathing problems or low blood pressure and need epinephrine immediately.
What are the most common food allergies?
In the US, nine foods cause most reactions: milk, egg, peanut, tree nuts, wheat, soy, fish, shellfish and sesame. Milk and egg are most common in young children, while shellfish is the most common in adults.
Can you develop a food allergy as an adult?
Yes. Adult-onset food allergies are common, especially to shellfish, fish, tree nuts and peanut. Some adults also develop oral allergy syndrome, an itchy mouth from raw fruits and vegetables linked to pollen allergy.
How is a food allergy tested?
An allergist combines your history with skin prick tests or blood tests for specific IgE. If results are unclear, a supervised oral food challenge confirms the diagnosis. Testing is only meaningful when guided by a history of reactions.
What is the difference between a food allergy and an intolerance?
A food allergy involves the immune system and can cause hives, swelling and life-threatening anaphylaxis, even from small amounts. A food intolerance, such as lactose intolerance, involves digestion and causes bloating or diarrhea but is not dangerous.
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
- American Academy of Allergy, Asthma & Immunology: Food allergy
- American College of Allergy, Asthma and Immunology: Food allergy
- FDA: Food allergies, what you need to know (FASTER Act)
- CDC: Food allergies in schools
- Food Allergy Research & Education (FARE): Facts and statistics