Inhibitory effect of chitosan-containing lotion on scratching response of hairless mice with atopic dermatitis-like dry skin

In this study, using a special diet-induced mouse model of atopic dermatitis, we tested the effect of chitosan-containing lotion (CL) on itch-related scratching associated with barrier-disrupted dry skin. HR-1 hairless mice fed a special diet exhibited apparent dry skin symptoms characterized by decreased skin hydration and increased transepidermal water loss. In the special diet-fed mice, scratching behavior was markedly enhanced for 60 min after oral administration of ethanol. When CL was applied once immediately after ethanol administration, the enhanced scratching response was significantly suppressed, but this effect was abolished within 30-40 min; when applied twice immediately and at 30 min, CL almost completely blocked scratching throughout 60 min. Comparison of CL and the chitosan-free vehicle showed that CL inhibited scratching more strongly and persistently than the vehicle, which transiently suppressed scratching only for 10 min after application. Although the decreased skin hydration was improved even by the vehicle, the increased transepidermal water loss was resolved only by CL. Skin surface temperature was much more reduced in CL-treated mice than in vehicle-treated mice. Collectively, CL has an antipruritic effect, which could be partly explained by recovery of skin barrier function and cooling of the skin.