hi painful blisters around mouth and ears are either infective or noninfective in aetiology. 1) infective cause viral cause e.g.herpes simplex(most commen) or other virus, bacterial cause e.g certain streptococcal bacterial infection. microscopica examination of the lesion will be useful in this variety 2)noninfective cause certain autoimmune disorders ( lupus,pemhigus etc.)may present with similar complains.for that you may require blood test to detect autoantibodies. treatment -it differs in both the above cases,for infective cause- antibacterial or antiviral may be required.while for non infective cause immuno supressant e.g. steroid, may be required.