Two foods that commonly cause brain allergies

People sometimes use brain allergy to describe headache, fogginess or feeling unwell after eating. Those symptoms have many possible explanations and do not prove an allergy. A true food allergy is an immune response to a food protein. Peanuts and shellfish are well-known triggers, but any food can cause a reaction. Symptoms may include hives, swelling, vomiting, wheezing or an itchy throat; [Food Allergy](/conditions/food-allergy/) explains the pattern.

An intolerance is different: it may cause digestive symptoms without the immune response seen in an allergy. Keeping a record of foods, amounts, timing and symptoms can help a clinician assess the pattern.

Stop eating the suspected food and avoid testing it again at home. Read ingredient labels and tell restaurants about the suspected allergy, while remembering that cross-contact can occur during preparation. Arrange medical assessment before removing many foods from your diet, particularly for a child. [Allergy Testing](/treatments/diagnostics-and-screening/allergy-testing/) may help identify a trigger, but results need to be interpreted with your history.

Call emergency services immediately for breathing difficulty, throat or tongue swelling, faintness, collapse, or symptoms affecting more than one body system after eating. These can signal [Anaphylaxis](/conditions/anaphylaxis/), which needs rapid treatment. Use a prescribed adrenaline auto-injector according to your action plan while waiting for help; [Anaphylaxis Emergency Treatment](/treatments/acute-and-urgent-care/anaphylaxis-emergency-treatment/) covers emergency care.

Ask whether your symptoms fit allergy, intolerance or another cause; which foods should be avoided; and whether you need an emergency action plan. Mention any [Itchy Throat](/symptoms/itchy-throat/) or reaction that occurred soon after eating.