External and internal exposure to the antigen in the hand eczema of nickel allergy.

A provocation study was performed in twelve female patients with contact allergy to nickel and hand eczema of the pompholyx type. Intense handling of nickle-contaminated metal objects did not induce any visible eczematous activity. Oral administration of nickle in a double-blind test provoked an aggravation of the hand eczema in nine of the twelve patients, and in seven of the patients this was accompanied by secondary eruptions including outbreaks of earlier, healed eczema. The nickle dose given is probably in the upper limit of the presently known daily intake of the metal, but should be considered to be within the physiologic range. It is concluded that ingestion of small amounts of nickel may be of greater importance in maintaining the hand eczema than external contacts with the metal.