Food allergy in adults
The prevalence of food allergy in adults is estimated to be about 3 percent compared to 15 to 40 percent frequency in children. Food allergy in adults can be due to two factors: (1) persistence of food allergy from childhood particularly allergy to peanuts/tree nuts which are usually life long conditions in most sufferers. Allergy to other foods in childhood rarely persists past age of 30 years, and (2) the development of new food allergies which develop spontaneously in adulthood. Once present, such food allergies tend to persist for a long time often for life unless appropriate avoidance measures are instituted.

In the case of the latter several factors predispose to new onset of food allergy in adults. Firstly, this include allergy to certain pollens (such as birch and ragweed pollens) with development of cross-sensitivity to allergens in certain fruits and vegetables. The symptoms often manifest as the "oral allergy syndrome" with local mucosal (lip or mouth symptoms) but not systemic symptoms. Secondly, occupational sensitization due to inhalation of food protein vapors during food processing or in cooking may sensitize the individual. Wheat flour allergy is increasing. However, "baker’s asthma" is generally due to inhalation of water-soluble wheat proteins (particularly albumins/globulins and also enzymes often added to the dough). Thirdly, sudden dietary changes with consumption of large amounts of a particular food after a period of abstinence can trigger an allergic reaction. Fourthly, concomitant intake of antacids with food causes inhibited catabolism of allergenic proteins in the gastrointestinal tract. As a result, large amounts of allergenic food components are more likely to be absorbed systemically initiating allergic reactions. Clinical manifestation of food allergy in adults can be quite varied with anaphylaxis and oral allergy syndrome as potential allergy problems. In Malaysia many adults with severe allergy problems and anaphylaxis have been noted to have allergy to all plant foods specifically pan-plant allergens. The diagnosis of food allergy in adults is similar to that in children and the trigger factors can be identified with initial search for IgE antibodies using the CAP RAST blood test.
A large number of adults also manifest ‘allergy-like conditions’ which on blood test indicate them to be ‘non-allergic hypersensitivity’. Many factors can be responsible for the development of these ‘allergy-like’ symptoms.