[Contact urticaria caused by skin test in pyrazolone allergy]

About one third of patients with anaphylactic reactions to pyrazolones showed contact urticaria induced by to at least one pyrazolone after 30-60 min in patch test. This reaction was never observed in patients with various exanthemas or allergic contact dermatitis to these medicaments. Contact urticaria in patch test was mostly caused by propyphenazone, aminophenazone, and metamizole. The suspicious pyrazolone provoked positive results in only about 70%. No correlation could be found between contact urticaria in patch test and severity of allergic history, short interval before skin test and atopic constitution.