Ultraviolet (UV) light does, in fact, kill ringworms! However, while ringworms cannot survive under prolonged exposure to UV light, of which natural sunlight is an excellent source, you should still seek medical attention if you have ringworm. Sunbathing may be a helpful supplemental treatment to medical care for ringworm, but it should not serve as a substitute. In many cases, what looks like ringworm may actually be a more serious medical condition, such as Lyme disease—as such, seeking the opinion of a verified medical doctor about a rash that appears to be ringworm should always be your first course of action. That said, if you have any objects that you have or might have ringworm on them, setting them out in the sun is a great way to disinfect them if throwing them away is not an option.