Food allergy is an abnormal immune reaction to food proteins, in which the body mistakenly treats them as dangerous. Manifestations can be mild, but in some people the reaction is life-threatening. Evaluation by a specialist helps distinguish allergy from intolerance.
What food allergy is
Normally, the immune system protects the body from microbes. In food allergy, it reacts to food proteins as if they posed a threat: immunoglobulin E binds to food molecules, which leads to the release of inflammatory substances, including histamine. That is why symptoms appear quickly.
Food allergy is confused with food intolerance. With intolerance, symptoms after eating also occur, but they are usually only digestive manifestations, and the immune system is not involved. Food allergy does not indicate a weak immune system: immunity does not decline, it overreacts.
The true prevalence of food allergy is about 1.5–2% in adults and approximately 6% in children. Significantly more people believe they have a food allergy, and some dietary restrictions arise without a confirmed diagnosis.
Symptoms of food allergy: rash on the skin and face
Symptoms usually occur within a few minutes to two hours after eating, sometimes later. They can affect any part of the body, and often several at once. The set of manifestations in one person is not always the same and depends on the amount of the food eaten.
A rash in food allergy most often looks like hives—itchy raised welts—or like redness of the skin. Food allergy on the face manifests as swelling of the lips, tongue, face, and eyes; tingling or itching in the mouth is possible. Skin symptoms are accompanied by itching and nasal congestion, and sneezing.
Respiratory manifestations include cough, wheezing, noisy breathing, and shortness of breath. Digestive manifestations include nausea, vomiting, abdominal pain, and diarrhea. Oral allergy syndrome is distinguished separately: itching in the mouth and throat after raw fruits, vegetables, or nuts.
Food allergic dermatitis
Skin manifestations of food allergy are an itchy rash or hives, as well as redness of the skin. They can occur together with other symptoms of the reaction, such as swelling of the lips and face or breathing problems.
The connection between the skin and food allergens also works in the opposite direction. Atopic dermatitis—inflammation of the skin with dryness, redness, and irritation—increases the risk of food allergy: through damaged skin, allergens penetrate the body more easily.
Which foods most often cause allergy
The set of allergenic foods depends on national dietary patterns. Most often, allergy in children is caused by chicken eggs and cow's milk; next come foods that are eaten frequently in the country: in China and Japan—seafood, wheat, and soy; in Israel—sesame; in the USA and Europe—peanuts.
- cow's milk and chicken eggs;
- peanuts, soy, peas, and chickpeas;
- nuts—walnuts, almonds, hazelnuts, cashews;
- crustaceans and mollusks, fish, wheat.
In Europe, the list is supplemented by sesame, lupin, celery, mustard, and sulfites. Allergy is possible to any food, so the search for the culprit is not limited to the list of common allergens.
How food allergy is diagnosed
The doctor asks about symptoms, when they appeared, foods eaten, and also about allergies, asthma, and eczema in the patient and their relatives. Then the doctor examines the patient and, if necessary, refers them to a specialist.
Skin prick tests are used, when a drop of liquid with the suspected allergen is applied to the skin and the reaction is assessed; blood tests for food antibodies; a diagnostic elimination diet; and an oral provocation test, which is considered the most accurate. A food and symptom diary is also helpful.
When urgent help and a doctor's visit are needed
Most symptoms of food allergy are not dangerous, but the reaction can be severe. A doctor is consulted when allergy is suspected in an adult or child; it is not customary to remove foods from the diet on one's own, because without evaluation it is easy to mistake the cause.
A rash alone is not a reason to call an ambulance; 103 or 112—if the lips, mouth, throat, or tongue suddenly swell, breathing becomes rapid or difficult, wheezing, suffocation, or a feeling of tightness in the throat appears, the skin, tongue, or lips turn blue or pale, confusion, drowsiness, or dizziness occurs, the person loses consciousness, or the child becomes lethargic.
Such signs indicate a serious allergic reaction, up to anaphylaxis with narrowing of the airways and a drop in blood pressure.
This material is for reference and does not replace a doctor's consultation: the examination plan is determined by a specialist.
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This content is for reference and does not replace a doctor's consultation. Medical disclaimer