Background A population-based twin study has recently shown that genetic factors are of significance for hand eczema.
Objectives To characterize further a sample of this twin material with regard to contact allergy, atopic dermatitis and wet work.
Methods In total, 1076 individual twins were examined clinically and patch tested. The diagnosis of atopic dermatitis was based on the U.K. Working Party criteria. The decision concerning wet work was based on the individual job description, taking into account the later introduced definition of at least 2 h of water exposure daily. The data were analysed by a newly developed statistical method which makes it possible to analyse the individual risk factor and at the same time discriminate between genetic and environmental factors.
Results The statistical analysis confirmed atopic dermatitis as an important risk factor for hand eczema. Contact allergy was also confirmed as a significant risk factor for hand eczema, and the risk was related to strength (+ to + + +) of contact allergy. The results indicated that the high frequency of hand eczema in women in comparison with men was caused by environmental and not genetic factors. Aggregation of hand eczema within twin pairs was only to a minor degree explained by atopic dermatitis and nickel allergy (or other contact allergies).
Conclusions We suggest that a hitherto unrecognized genetic risk factor for hand eczema independent of atopic dermatitis and contact allergy is probably of importance for the development of irritant contact dermatitis on the hands.