What causes allergies?

I guess it is more like in asthma, First the person will be expose to any allergen like pollens, dusts, sea foods.Mast cells in the body play a major role to this. If some exposed to allergen, allergen binds to Immunoglobulin E (IGE) then mast cells are activated it release granules and chemical mediators like histamine 1 which triggers inflammatory response like redness and swelling. It causes vasodilation or blood vessels dilate so people will have redness in some parts of the body,bronchial constriction or the bronchi in the lungs constrict so there is difficulty breathing;if persist can cause anaphylactic shock. If your brother is allergic to prawns, he should tell the doctor before undergoing some medical procedures that require dye injection like contrast MRI,CT-scan with contrast and angiography. For he may be allergic to iodine. These procedures are contraindicated to him. if he is exposed to allergens and develop allergy, he should at least take ANTIHISTAMINE medications, and if his reaction is worst like he has difficulty breathing when exposed to allergens, then he should consult a doctor so he can prescribe EPINEPHRINE. The most natural is that, he should know what substances that he is allergic to and then STAY AWAY from those as much as possible.

I was suppose to explain something about the IGE or the Immunogloblulin E that causes allergies. Anyway, I think the first respondent made it all clear now. Anyway, I hope your brother will be able get over his allergies.

I think we have NURSES here or perhaps studied in a medical school.All your questions are already answered. I'm wondering now if there's a physician who joined mylot. Hmmm.... Anyway, there's a test to identify your allergies(most of the time we are not aware that we have allergies to this and that until it is triggered). Just visit your physician.