IRRITANT SUSCEPTIBILITY AND WEAL AND FLARE REACTIONS TO BIOACTIVE AGENTS IN ATOPIC-DERMATITIS .1. INFLUENCE OF DISEASE SEVERITY

The two main pathogenetic characteristics of atopic dermatitis (AD) ar e: (i) antigen-dependent 'specific' reactivity, and (ii) altered non-i mmunological 'non-specific' reactivity, Our understanding of the role of non-specific reactivity is hampered by the fact that methods availa ble for its quantification are limited. The aim of the present study w as to assess the usefulness of two parameters as quantitative measures of non-specific skin reactivity in AD: (i) susceptibility to repeated epicutaneous exposure to an irritant (sodium lauryl sulphate, SLS), a ssessed by visual scoring and transepidermal water loss (TEWL) measure ment, and (ii) reactivity to intracutaneously injected bioactive agent s (codeine, FMLP, histamine, methacholine, substance P, trypsin), asse ssed by measurement of weal and flare size. These two parameters were tested in a group of AD patients, subdivided according to the severity of their dermatitis, and a control group, The visual score and TEWL a fter SLS exposure tended to be higher in the AD group than in the cont rol group. Furthermore, visual score and post-exposure TEWL were posit ively correlated with the dermatitis severity score. Weal size followi ng injection of codeine, histamine and substance P, and flare size fol lowing injection of all agents, except methacholine, were significantl y lower in the AD group than in the control group. Negative correlatio ns were found between weal and flare sizes and the dermatitis severity score. These findings can be explained by down-regulation of structur es involved in weal and flare reactions. In conclusion, we propose tha t epicutaneous irritant susceptibility and reactivity to intracutaneou s bioactive agents may be useful indicators of non-specific skin react ivity in AD.