Food Allergy

Original source overview

What is a food allergy?A food allergy is an abnormal immune system reaction to certain foods. Your immune system normally protects you from germs. But if you have a food allergy, your immune system mistakenly reacts to certain foods as if they were harmful. This reaction is usually mild. But in some cases, it can be serious or even life-threatening.

A food intolerance is different than a food allergy. If you have a food intolerance, you also have symptoms when you eat that food. But these are typically just digestive symptoms such as bloating and gas. Also, an intolerance is not an immune system reaction.

Most food allergies are caused by:

• Cow's milk • Chicken eggs • Crustacean shellfish, such as shrimp, crab, lobster, and crayfish • Fish • Peanuts • Sesame • Soy • Tree nuts, such as almonds, walnuts, pecans • Wheat

People with a food allergy may be allergic to more than one type of food.

Who is more likely to develop a food allergy?Both children and adults can have food allergies. Some children will outgrow their food allergies. And sometimes people can develop food allergies as adult.

Certain factors can make you more likely to have a food allergy. They include:

• Having eczema, a disease that causes inflammation, redness, and irritation of the skin. Your immune system also plays a role in eczema. • Having asthma or other allergies, such as hay fever. • Your genes. Certain genes may influence the development of food allergies. And you are more likely to have food allergies if someone in your family has allergies, asthma, or eczema.

What are the symptoms of food allergies?If you are allergic to a food you have eaten, you may have a variety of symptoms. These symptoms are not always the same for every person. And the symptoms that you get each time you eat the food may not always be the same. For example, your symptoms may sometimes depend on how much of the food you ate.

Food allergy symptoms usually start within a few minutes to two hours after you eat that food. They may include:

• Hives • Flushed skin or rash • Tingling or itchy sensation in the mouth • Face, tongue, or lip swelling • Vomiting and/or diarrhea • Abdominal (belly) cramps • Coughing or wheezing • Dizziness and/or lightheadedness • Swelling of the throat and vocal cords • Trouble breathing

In rare cases, a food allergy can cause a life-threatening reaction called anaphylaxis. It may start out with some milder symptoms, but then it becomes more serious. It can lead to:

• Narrowed airways in the lungs • Severe trouble breathing because of swelling in the throat • Severe lowering of blood pressure and shock ("anaphylactic shock") • Loss of consciousness

This is a medical emergency. Call 911 if someone is having the symptoms of anaphylaxis.

How are food allergies diagnosed?To find out if you have a food allergy, your health care provider will

• Ask about your symptoms, family health history, and medical history, including other allergies. • Likely do a physical exam. • Do food allergy testing. This could involve skin testing, blood testing, a food elimination diet, and/or an oral food challenge test. An oral food challenge test is the most accurate food allergy test.

What are the treatments for food allergies?There is no cure for food allergies. The only way to prevent a reaction is to avoid eating the food that you are allergic to.

There are medicines for people with food allergies. They include:

• Medicines to reduce food allergy symptoms, including antihistamines and corticosteroids. • Medicines to reduce allergic reactions, including severe reactions. • Epinephrine, a medicine to treat anaphylaxis. Your provider may give you a prescription for an epinephrine auto-injector. It is a device used to inject epinephrine when someone is having symptoms of anaphylaxis. If you have been prescribed one, it's important to learn how to use it and to carry it with you at all times.

If you have a food allergy, it's a good idea to have a medical alert bracelet that says what your allergy is.

Encyclopedic background — Wikipedia

The following selected excerpts provide background on “Food allergy”. The scope here is Food Allergy; it does not establish an individual diagnosis or treatment plan. They are not a substitute for the source overview or current local clinical guidance. Each excerpt below comes from the fixed Wikipedia revision [W1].

Definition and overview [W1]

A food allergy is an abnormal immune response to food. The symptoms of the allergic reaction may range from mild to severe. They may include itchiness, swelling of the tongue, vomiting, diarrhea, hives, trouble breathing, or low blood pressure. This typically occurs within minutes to several hours of exposure. When the symptoms are severe, it is known as anaphylaxis. A food intolerance and food poisoning are separate conditions, not due to an immune response.

Common foods involved include cow's milk, peanuts, eggs, shellfish, fish, tree nuts, soy, wheat, and sesame. The common allergies vary depending on the country. Risk factors include a family history of allergies, vitamin D deficiency, obesity, and high levels of cleanliness. Allergies occur when immunoglobulin E (IgE), part of the body's immune system, binds to molecules in food, usually proteins. This triggers the release of inflammatory chemicals such as histamine. Diagnosis is usually based on a medical history, elimination diet, skin prick test, blood tests for food-specific IgE antibodies, or oral food challenge.

Management involves avoiding the food in question and having a plan if exposure occurs. This plan may include giving adrenaline (epinephrine) and wearing medical alert jewelry. Early childhood exposure to potential allergens may be protective against later development of a food allergy. The benefits of allergen immunotherapy for treating food allergies are not proven, thus not recommended as of 2015. Some types of food allergies among children resolve with age, including those to milk, eggs, and soy; while others such as to nuts and shellfish typically do not.

Signs and symptoms [W1]

A severe case of an allergic reaction, caused by symptoms affecting the respiratory tract and blood circulation, is called anaphylaxis. When symptoms are related to a drop in blood pressure, the person is said to be in anaphylactic shock. Anaphylaxis occurs when IgE antibodies are involved, and areas of the body that are not in direct contact with the food become affected and show symptoms. Those with asthma or an allergy to peanuts, tree nuts, or seafood are at greater risk for anaphylaxis.

Causes [W1]

The most common food allergies are those to milk, egg, peanuts, tree nuts, fish, shellfish, soy, and wheat, which are referred to as "the big eight", and are required by US law to be on labels of foods that contain those foods. In April 2021, President Biden signed the FASTER Act into law. This recognized sesame as the ninth US mandatory food label allergen.

Egg allergies affect about one in 50 children but are frequently outgrown when children reach age five. Affected individuals can be sensitive to proteins both in the egg white and egg yolk, but most children are allergic to those in the white while most adults are allergic to those in the yolk.

Balsam of Peru, which is in various foods, is in the top five allergens most commonly causing patch test reactions in people referred to dermatology clinics.

Pathophysiology [W1]

Conditions caused by food allergies are classified into three groups according to the mechanism of the allergic response:

IgE-mediated (classic): the most common type, occurs shortly after eating and may involve anaphylaxis.

Non-IgE mediated: characterized by an immune response not involving immunoglobulin E; may occur some hours after eating, complicating diagnosis.

Reading this topic in context

Use “Food Allergy” as a starting point for a focused discussion, rather than treating every statement in the broader encyclopedia article as applying to you. The original source overview and the background excerpts answer different questions: the overview explains the health topic for readers, while the encyclopedia supplies terminology and general context. Keep a record of which questions concern symptoms, a confirmed diagnosis, prevention, or an existing treatment. This helps a healthcare professional address the relevant issue without relying on an internet label.

Questions to take to a professional

1. Is this likely to be an allergy or another food-related problem?

2. What testing, avoidance advice and emergency plan are appropriate?

Evidence, scope and next steps

The health-topic overview is attributed to MedlinePlus / the National Library of Medicine at the original topic link below. Wikipedia [W1] is a secondary background source; its references can support further reading, but their presence is not evidence that WellPrimer has independently reviewed every study. No clinical review, guideline certification or NLM endorsement is claimed. For screening intervals, diagnostic thresholds, pregnancy or child-specific advice and treatment choices, check current guidance in your country with a qualified professional. Do not start, stop or change a prescribed medicine based on encyclopedia excerpts. New or worsening symptoms need appropriate clinical assessment rather than more reading alone.

Attribution and reuse

[W1] Wikipedia contributors, “Food allergy”. Version 1375989509, edited 2026-09-21. Retrieved 2026-10-16. Fixed revision: https://en.wikipedia.org/w/index.php?title=Food_allergy&oldid=1375989509. Contributor history: https://en.wikipedia.org/w/index.php?title=Food_allergy&action=history. License: https://creativecommons.org/licenses/by-sa/4.0/ .

The MedlinePlus health-topic summary retains its original attribution. Wikipedia excerpts and the added compilation/commentary are shared under CC BY-SA 4.0; selections, section ordering and editorial reading prompts have been added. No images are reused. This is an educational compilation, not a clinician-reviewed guideline.