A skin fungus is an infection of the skin by a fungus, a microorganism that usually consumes dead material. The outer skin is made up of dead skin cells that form a barrier to the outside environment. This barrier is usually able to maintain its own health but if damaged (especially by breaks or a cut in the skin), it can be prone to infections. There are certain types of fungi – dermatophytes (molds) and yeasts - which can quickly invade and establish itself on the skin surface in the optimal settings.