Described are methods, kits, apparatus, and compositions for integumentary system therapy. For example, a method for therapy may include providing a subject in need of therapy for a condition. The condition may be associated with a substrate located in the subject's integumentary system. The method may include contacting a therapeutic agent and the substrate in the subject's integumentary system. The method may include modulating a depth of at least one ionic species in the subject's integumentary system. The at least one ionic species may include one or more of: the therapeutic agent； a bound therapeutic agent:substrate complex； and a reaction product of one or both of the therapeutic agent and the substrate. The method may be effective to at least partly ameliorate the condition in the subject.
