Food allergies occur when the immune system reacts abnormally to proteins in certain foods. Reactions can range from relatively mild symptoms, such as hives or swelling, to anaphylaxis, a potentially life-threatening reaction that can affect breathing and blood pressure.
Food allergy is different from food intolerance. An allergy involves the immune system, while many food intolerances do not. Food allergies can also involve different immune pathways, so not every food-allergic reaction is mediated by immunoglobulin E, or IgE.
Common triggers
Many foods can cause allergic reactions, but the major allergens vary by country and food-labeling system.
In the United States, the Food and Drug Administration recognises nine major food allergens: milk, eggs, fish, crustacean shellfish, tree nuts, peanuts, wheat, soybeans and sesame. Sesame became the ninth major allergen under U.S. law in 2023.
These foods account for the large majority of serious food-allergic reactions covered by U.S. allergen-labeling rules. Other foods can also cause allergies, however, so a person should not assume that a food is safe simply because it is not on a particular country’s list of major allergens.
Symptoms can affect several parts of the body
Food-allergy symptoms may develop within minutes or several hours after exposure. They can include hives, itching, swelling of the lips or tongue, vomiting and other gastrointestinal symptoms. More serious reactions can cause difficulty breathing, throat tightening, a drop in blood pressure or other signs of anaphylaxis.
Anaphylaxis requires immediate medical attention. People who have been diagnosed with a food allergy that can cause severe reactions are commonly given an emergency treatment plan that includes epinephrine, also known as adrenaline.
How food allergies are diagnosed
Diagnosis begins with a medical history and an assessment of what happened after eating a suspected food. An allergy specialist may use skin-prick or blood tests to look for evidence of sensitisation to particular allergens.
Those tests do not, by themselves, prove that a person has a clinical food allergy. Depending on the circumstances, a doctor may use a medically supervised oral food challenge, in which a patient consumes controlled amounts of the suspected food under medical observation, to help establish whether an allergy is present.
This distinction is important because a positive allergy test can indicate sensitisation without necessarily meaning that eating the food will cause an allergic reaction.
Managing a food allergy
For people with a confirmed food allergy, avoiding the identified allergen remains a central part of management. This can require checking ingredient lists, asking about ingredients when eating food prepared by others and taking precautions against accidental exposure.
Food labels can help consumers identify major allergens in packaged products. In the United States, federal rules require most FDA-regulated packaged foods to identify ingredients containing the nine major allergens.
People with a history of severe allergic reactions should follow the emergency plan provided by their healthcare professional and have prescribed emergency medication available when advised.
Food allergy remains a significant health issue
Recent U.S. data illustrate the prevalence of the condition. In 2024, 6.7% of adults and 5.3% of children aged 0 to 17 in the United States had a diagnosed food allergy, according to the CDC’s National Center for Health Statistics. Among children, diagnosed food allergy increased from 3.9% among those aged 0 to 5 to 6.9% among those aged 12 to 17.
The figures are U.S.-specific and should not be treated as a global prevalence estimate. They nevertheless show why accurate diagnosis, allergen avoidance and emergency preparedness remain important parts of managing food allergies.
For anyone who develops symptoms after eating a particular food, especially breathing difficulty, throat swelling, weakness or other signs of a severe reaction, medical care should be sought urgently rather than relying on self-diagnosis.
