Mast cells and their mediator, histamine, are well-recognized effectors in immediate allergy, but their role in tissue remodeling and chronic inflammation has also been the focus of intense research during the past decade. Gschwandtner et al. (2008, this issue) report that histamine can induce MMP-9 expression in keratinocytes, promote collagen type IV degradation in the basement membrane, and stimulate keratinocytes, leading to increased T-cell transmigration through an artificial basement membrane.