A primary doctor, or a dermatologist, can look at it in order to tell what it is. If dry skin
or eczema rash
, Hydrocortisone cream
helps. Some rashes are an allergy to something. Hydrocortisone also helps allergic rashes. Ringworm fungus
would need an antifungal. If it doesn't go away, a dermatologist can tell if it is something serious.