Metal contact sites: a hidden localization for nail varnish allergy?

It is thought that many people with nickel dermatitis use nail varnish as a barrier coat on nickel-containing metals; however, nail varnish allergy at sites in contact with such coated has only been documented once previously, to our knowledge. The aim of this study was to search for a possible link between nail varnish and metal allergy. In total, 1607 consecutively patch-tested patients were enrolled; 16 (1%) of these had nail varnish allergy, located mainly on the eyelids. Eight also had nickel allergy. Six of these eight had successfully used protective nail varnish on metals until subsequent development of 'failure of protection' even before the eyelid eczema developed. Sites in contact with metal might be a hidden and even initial localization for nail varnish allergy. 'Failure of protection' after a successful protective period despite renewing nail varnish coatings should raise suspicion of sensitization to the nail varnish itself. Future studies should focus on the incidence of allergic contact dermatitis and primary sensitization from nail varnish used as a barrier against nickel dermatitis.