Retesting with the TRUE Test in a population-based twin cohort with hand eczema - allergies and persistence in an 8-year follow-up study.

Population-based studies on contact allergy with retesting of individuals are infrequently performed. Variable degrees of persistence are reported when individuals with contact allergy are retested with years in between. The patch test results of 270 individuals tested in 2005-2006 are presented and the pattern and frequency of sensitization discussed. Persistence when compared with patch test results from 1997-1998 is reported. 270 twin individuals with and without hand eczema underwent patch testing with the TRUE Test((R)) (Mekos Laboratories AS, Hilleroed, Denmark) in 1997-1998 and again in 2005-2006 as part of a larger study. In 2005-2006, a total of 74 (27.4%) of the 270 individuals had at least 1 positive patch test and 20 (7.4%) of the 270 had 2. The frequency in men and women was 9/90 (10%) and 65/180 (36.1%), respectively. The frequency of contact allergy in individuals with and without hand eczema was 59/185 (31.3%) and 15/85 (17.6%), respectively. The most prevalent contact allergies were to nickel, thiomersal, and fragrance mix I. All together, 74% of the positive reactions were reproduced. The frequency of contact allergy in this population-based cohort with hand eczema was comparable with previous reports. Persistence of contact allergy after many years was confirmed.