The symptoms most often appear immediately (within minutes or seconds) after food intake. They may involve itching of the palate, lips or throat, swelling of lips, tongue or pharynx, rhinitis, conjunctivitis or asthma. I t can also be an attack of generalized urticaria, an angioedema, anaphylactic shock. Manifestations of chronic eczema are as well possible, especially in children. Thus, in infants younger than one year, a quarter of generalized eczema is due to peanuts. Peanut tops the list of foods implicated in small, by its frequency and severity. Other foods most allergenic in children are egged, milk, mustard and fish. In adults, it is in order, sesame, fish and peanut. The association with an allergy to pollen or latex is common.
If the doctor can often recognize an allergy by clinical examination and examination of his patient, additional tests are sometimes needed to confirm the diagnosis and determine the list of offending allergens. Blood samples, assaying certain antibodies may indicate an allergic and direct them to one or more allergens. These can also be tested directly: on the skin, respiratory tract ... The idea is to see if they trigger the same experimental re action that the patient presented spontaneously. In general, we test a battery of products: those who are suspected in the case of the patient and a series of standards called allergens, that is to say, in often implicated in allergies.
There are two types of skin tests, prick tests and patch tests. For prick tests, the allergist injected very low doses of allergens under the skin of the arms, and it checks after about twenty minutes if some bite trigger inflammation. The patch tests them, performed in the plating substances on the skin at the back. The local reaction is checked after 48 hours.