Background The etiology of urticaria is often difficult to determine. However, in case of repeated circumsance-connected urticaria, the reason may be easily clarifyable.

Case A 51-year-old healthy woman repeatedly experienced occupational hand urticaria when handling fish food. An unexpected reason for the urticaria was found in that the fishfood contained histamine as a "contaminant".

Conclusions In fishfood batches, biological degradation can produce histamine and possibly other toxic substances that can lead to occupational health problems.

Key terms contamination; histamine