Fragrance-mix and balsam of Peru were the commonest contact sensitizers. In some patients with urticaria, whealing occurs within minutes of the ingestion of a particular food. In most, but not necessarily all cases, this appears to be a consequence of IgE-mediated cutaneous mast cell degranulation, i.e. a classical type I hypersensitivity response. In other patients with recurrent urticaria, the whealing may be provoked by foods by a much slower and more insidious reaction. This type of reaction has been established in the case of several common food additives, notably azo dyes, but other foods may be able to cause urticaria in a similar fashion.
Foods appear to play an important provocative role in many patients with atopic eczema.
The reaction in such cases appears to be slow and insidious, almost always unrecognized by the patient and not detected by skin testing or tests for IgE antibodies. There can be no real doubt that dietary gluten is responsible for most, if not all dermatitis herpetiformis, though this relationship was revealed only by the finding of concurrent and usually asymptomatic jejunal villous atrophy in affected individuals. The mechanisms responsible for the slow food reactions in urticaria, atopic eczema and dermatitis herpetiformis remain largely unknown, but are likely to be different in each case.