掻痒性皮膚疾患の外用療法と薬局薬剤師の役割

Itching, or pruritus, can be defined as an unpleasant sensation that evokes the desire to scratch. Pruritus is most commonly associated with a primary skin disorder such as atopic dermatitis (AD), psoriasis, etc., and can have a major impact on the quality of life of those patients. Itch-induced scratching can further damage the skin barrier, leading to a worsening of symptoms. For that reason, it is important to manage pruritus. Topical glucocorticoids are commonly the first-line therapy in the management of AD and psoriasis patients. We found that topical glucocorticoids induce pruritus in mice under certain conditions. Topical glucocorticoids may induce pruritus in a mouse model of allergic contact dermatitis via inhibition of prostaglandin (PG)D₂ production in antigen-mediated activated mast cells in the skin. Additionally, topical glucocorticoids do not induce pruritus in healthy skin. These results indicate the importance of controlling skin infiammation to a healthy level by applying sufficient quantities of glucocorticoids to avoid glucocorticoid-induced pruritus. However, topical ``steroid phobia'' is common in Japan, and most patients apply inadequate amounts of topical glucocorticoids for this reason. This may cause glucocorticoid-induced pruritus in patients by prolonging the skin infiammation. We conducted a survey regarding community pharmacists' instructions on the application quantity of topical glucocorticoids and found that most community pharmacists have experienced inappropriate instructions concerning this point.