Risk factors of polysensitization to contact allergens

'Polysensitization' (PS) is usually defined as contact sensitization to three or more unrelated haptens of the baseline patch test series. Despite PS being an important clinical phenotype indicating increased susceptibility to contact allergy, statistical approaches to analyse PS have hitherto been preliminary.

To apply an appropriate regression model for count data, namely, negative binomial hurdle regression, to a large set of clinical patch test data with the aim of estimating PS risk in more detail than previously achieved.

The detailed information provided by the hurdle model includes a separate estimation of an 'increment factor' quantifying the likelihood of further positive reactions, i.e. PS. Clinical data of 126 878 patients patch tested by departments comprising the IVDK (Information Network of Departments of Dermatology) network (www.ivdk.org) between 1995 and 2010 were included.

Regarding anatomical sites as exposure (surrogate), the axillae and the feet were found to be strong PS risk factors. Moreover, age was a strong PS risk factor, and less so, female sex. In comparison, atopic eczema and occupational dermatitis were less important risk factors. Single allergens contributed to PS to a varying extent.

The data presented point to some, very likely exposure-related, risk factors which need to be considered in future PS research, e.g. addressing the genetic basis for PS.