The specificity of a nickel sulphate reaction in vitro: a family study and a study of chromium-allergic subjects.

In vitro PPD and nickel sulphate lymphocyte blast transformation reactions were performed in ten families with one or more allergic nickel contact dermatitis patients. The healthy family members did not have an inherited ability to react to nickel in vitro. Their nickel stimulation response was significantly lower (P less than 0.005) than that among the allergic subjects. In the families studied, atopic members did not have higher nickel reactions than nonatopic subjects. Thus, the in vitro nickel reaction is not connected to atopy. This is further confirmed by the fact that the percentage of atopic subjects (19%) in these families is not higher than the percentage in the general population. In addition, six unrelated chromium-allergic patients were tested, and their lymphocytes did not cross-react with nickel sulphate in vitro. These results indicate that the in vitro nickel blast transformation reaction is specific to clinical nickel allergy in about 90% of nickel dermatitis patients.