No abstract

Sera from nearly all ASST-positive patients with CU are able to induce histamine release in vitro. However, the serum from each single patient seems to show its maximal activity on autologous mast cells in vivo, and functional in vitro tests show much variability and seem less sensitive than ASST in the detection of patients with histamine-releasing factors in their blood.

In urticaria, adverse reactions to food are only a frequent finding in the subset of patients with chronic continuous urticaria. Mostly these reactions are of pseudoallergic nature, directed against artificial additives as well as naturally occurring aromatic components. IgE-mediated allergic reactions are a rare cause in acute urticaria as well as in recurrent chronic urticaria. In other types of urticaria, e.g. physical urticaria, food plays hardly any role as an eliciting agent with the exception of ice-cold drinks in cold urticaria. By contrast, exercise-induced anaphylaxis is frequently food-dependent. Two subtypes are distinguished: unspecific food-dependent exercise-induced anaphylaxis (FDEIA), where the filling of the stomach independently of the kind of food ingested prior to exercise is responsible for the symptoms. In specific FDEIA, an IgE-mediated food allergy causes symptoms only in combination with exercise. In the latter group, wheat is an important allergen.