The hidden sense of symptoms: urticaria can be beneficial

Evolutionary Medicine can be useful when analysing the origin of disease and symptoms. Acute urticaria or anaphylaxis is bothersome and potentially life-threatening. We analyse this symptom-complex in the context of Gastro-allergic Anisakiasis (GAA), where the human is an incidental host for the cosmopolitan fish-nematode Anisakis simplex (A. simplex). The immunological response against this nematode resembles that against other helminths, but overt expression of allergic symptoms is by far more frequent in GAA. This could be due to the missing co-evolutionary relationship between host and parasite. Features of acute gastric parasitism with and without overt allergic type 1 hypersensitivity symptoms are compared with the abdominal complications in intestinal Anisakiasis, where clinically visible IgE mediated symptoms are missing. In GAA, parasite induced chronic abdominal complications are missing. We postulate that urticaria in GAA can be considered the price for rapidly expelling the live larva of A. simplex in those subjects whose evolutionary history made them more resistant to other helminth parasites. Further, urticaria is explained as a possibly exaggerated immunopathological feature in this special type of acute parasitism, where sensitized mast-cells are not only present in the skin, but also in the gastro-intestinal mucosa. This evolutionary analysis of clinical observations is the first known report that addresses the possible beneficial feature of hypersensitivity type 1 response with overt allergic urticaria-anaphylaxis in GAA and confers an evolutionary based sense to the acute IgE-mediated reaction.