Ringworm vs nummular eczema: Ringworm often starts out as a solid, circular red patch with a fine scale and it will evolve into a ring with raised border and central clearing. Nummular eczema will be solid circular lesions, also with scale but no central clearing. When in doubt, put hydrocortisone on it. If it starts to improve, it's likely eczema (or an eczema-like rash). If it gets way worse, it's likely ringworm and you should put clotrimazole on it.