Loss of contact sensitization evaluated by laser Doppler blood flowmetry and transepidermal water loss measurement.

Allergic contact dermatitis, which is mediated by activated T cells through a Type IV reaction, is usually believed to persist throughout life. There have been several reports of spontaneous loss of sensitization, e.g., loss of previous patch test reaction or loss of allergic contact dermatitis withal continuous exposure to the allergens. However, these have been well quantified. The aim of this study was to confirm the development of desensitization or hyposensitization with the aid of objective measurements. A total of 18 patients with alopecia areata, who received 4 months diphenylcyclopropenone (DPCP) contact immunotherapy, were patch tested and the responses were measured by laser Doppler blood flowmetry (LDF) and transepidermal water loss (TEWL). Patch tests were performed 2X, before and after 4 months of immunotherapy. To determine whether local desensitization developed, we compared change of DPCP concentrations producing mild contact dermatitis on the scalp. Our results showed that systemic and local hyposensitization occurred in human subjects by weekly applications of low concentrations of DPCP for 4 months. LDF seems to be more correlated with visual scores than TEWL measurement.