Members of the interleukin-17 (IL-17) family of proinflammatory cytokines are important in the immune response to infections. However, too much IL-17 signaling is associated with autoimmune inflammatory diseases, such as asthma, psoriasis, and rheumatoid arthritis. Liu et al. performed small-molecule screening to look for compounds that could bind to the IL-17 receptor. They found that cyanidin, a flavonoid found in red berries and other fruits, bound to the IL-17 receptor and blocked the binding of IL-17A. In several mouse models of inflammatory disease, cyanidin alleviated the inflammation induced by IL-17A–producing T cells.