Many people have a food allergy. Although they are more common in infants and children, they can still appear later in life. A food allergy is a reaction that occurs when your immune system overreacts to a food or a specific substance in a food. The most severe type of food allergy is anaphylaxis, which occurs when multiple organ systems in the body are affected. During anaphylaxis, your breathing is impaired and your blood pressure and heart rate drop rapidly, which can be fatal. Interestingly, 90% of all food allergies can be attributed to 8 types of food: peanuts, tree nuts, milk, soy, wheat, fish, shellfish, and eggs. Seeds are also a common food allergy.
Food Allergy Versus Food Intolerance
While food allergy and food intolerance can have some similar symptoms, there is a clear difference between the two responses. Food allergy can be fatal because it can cause anaphylaxis while food intolerance is generally less severe. Food Intolerance involves the digestive system whereas food allergy affects the immune system.
Some people experience mouth itchiness and tongue or lip swelling after eating raw vegetables, fruits, and tree nuts. This is called oral allergy syndrome, and it occurs because the immune system has identified proteins and pollen found in the raw food as allergens. Although the symptoms of oral allergy syndrome occur as a result of eating food, it is not a food allergy but rather a pollen allergy. Unlike food allergy, the symptoms of oral allergy syndrome are not long lasting and usually resolve once the raw food is digested. Most people with oral food allergy will have no problems eating the same fruits, vegetables, and tree nuts in cooked form because the proteins and pollen are changed by heat.
Symptoms of food allergy often begin within minutes. Most symptoms occur within 2 hours of food ingestion. It is very rare, although possible, to experience a delayed reaction where symptoms occur more than several hours later. Food allergy symptoms may affect many parts of the body, including the gastrointestinal tract, skin, respiratory tract, and cardiovascular system. Signs of food allergy include:
- Respiratory: Shortness of breath, wheezing, cough, difficulty swallowing, tight throat, and tongue swelling
- Skin: Hives, itch, pale or blue skin coloring
- Gastrointestinal: stomach cramps, vomiting
- Cardiovascular: circulatory shock, weak pulse, dizziness or faintness
A severe reaction to a food allergen can cause anaphylaxis in which multiple organ systems are affected and the body goes into shock. Anaphylaxis involves a rapid decrease in blood pressure, weak but rapid pulse, airway narrowing, skin rash, and nausea or vomiting. Anaphylaxis requires emergency medical attention.
Every allergy diagnosis starts with a detailed medical history and physical examination. From there, your allergist may elect to order several diagnostic tests.
Your allergist may perform a skin-prick test where small volumes of food allergens (and controls) are pushed into your skin with a sterile needle. After 20 minutes, the skin is re-examined for any wheals, or bumps. A blood test can measure the amount of IgE antibody circulating in the blood in reaction to the specific food allergen of interest.
Your allergist may ask you to consume a small amount of the suspected food allergen in a supervised, medical setting. This is done to confirm an allergy or to verify you have outgrown one.
Food Allergy Treatment & Management
To prevent allergic reactions to trigger foods, it is important to know the ingredients of all foods you eat. Whether you are buying food from a store or ordering food from a restaurant, always read the food labels and ask about ingredients.
Managing a Food Allergy Reaction
For mild food reactions, antihistamines can relieve symptoms. Severe allergic reactions may require injection with epinephrine (adrenaline), so be sure to have an EpiPen with you at all times and know how to use it.
Immunotherapies Under Investigation
Although avoidance is currently the safest and most effective way to protect against food allergy, the FDA is investigating new immunotherapies to help individuals become less sensitive to certain foods. One therapy that is being studied involves introducing small doses of food allergen into the skin via a patch. Another involves an oral tablet that contains a small amount of food allergen.
 American College of Allergy, Asthma & Immunology: https://acaai.org/  Asthma and Allergy Foundation of America: https://www.aafa.org/