If one has crotch itch, apply some vinegar to the area. If it stings, then vinegar kills tinea corporis. If it does not sting, that means that either there is no tinea corporis infection on the skin, or vinegar is not strong enough to kill the infection. If it does not sting, use hydrogen peroxide or baking soda. If hydrogen peroxide and baking soda cause stinging, then they are killing the tinea corporis.