Frequency of delayed-type hypersensitivity to contact allergens in palmo-plantar psoriasis

Psoriasis is a common, chronic, genetically determined, T-cell-mediated inflammatory dermatosis. The aim of this study is to determine the frequency of delayed-type hypersensitivity to contact allergens in palmo-plantar psoriasis and their importance in provoking and/or perpetuating the same.

101 patients with different clinical forms of psoriasis were included in our study. The patients were divided into two groups, on the base of the clinical aspects and localizations of the lesions. The first group consisted of 38 patients with palmo-plantar psoriasis. The second, control, group of patients with psoriasis vulgaris but without lesions on palms and soles included 63 cases. The patch-tests were performed on all 101 patients.

In the first group of patients with palmo-plantar psoriasis, the patch-tests were positive in 15 patients (39.5%). Only 8 patients (12.7%) had positive results of patch-testing in the control group (psoriasis without palmoplantar involvement). The study showed a highly statistically significant difference in the frequency of positive patch-tests between the two investigative groups (p < 0.01). In the first group of patients with palmo-plantar psoriasis there was noted a statistically significant greater number of positive patch-tests.

The results of our study showed a statistically significant bigger number of positive patch-tests in patients with palmo-plantar psoriasis, which confirmed the role of contact allergens in the triggering and/or perpetuating of the lesions. Therefore, it is necessary for patch-testing to be included as a diagnostic procedure in patients with psoriasis unresponsive to conventional topical treatment. It is possible that avoiding selected antigens may alleviate chronic, recalcitrant psoriasis.