Tinea cruris is a fungal infection of the groin and the perineum, i.e., the crotch. Wash with heavy soap again and again, then dry the area and apply hydrogen peroxide which will burn like hell, or apply a lot of baby powder to keep the area dry, or apply a generous amount of petroleum jelly, vasoline, on the crotch to stop the itch and smooth the skin. If the skin of the crutch area becomes scaly and rough, scrub the area with a rough dishwasing scrub pad, then wash with heavy soap, then clean with hydrogen peroxide. It is important to keep the crotch area dry. Briefs, underwear, panties, even wrapping oneself with a beach towel will moisten the crotch area, and the tinea cruris or fungal infection will return.