The doctor will ask questions about your symptoms to rule out other conditions. She/he will also try to figure out what has triggered the erythema multiforme, e. g another illness or some medications. She/he will then examine your rash. This may be enough to make a diagnosis. However, in some cases, She/he may need to get a small sample of skin so that the lesions can be looked at under a microscope.
Attribution: Avallain