<unk>  is a skin condition of unknown etiology, but some authors suggest that the disease is mediated by deposition of immune complex (mostly IgM) in the superficial microvasculature of the skin and oral mucous membrane. It can occur due to drug exposure,as well in association with some types of infections. It varies from a mild, self-limited rash (E.<unk>  minor) to a severe, life-threatening form (E.<unk>  major, or Stevens-Johnson syndrome) that also involves mucous membranes.
E.<unk>  may also be caused by drug reactions, most commonly sulfa drugs, Hydrochlorothiazide,  phenytoin, barbiturates, penicillin, and allopurinol, Ethynodiol diacetate and ethinyl estradiol, or a host of internal ailments. The most common predisposing infection for E.<unk>  is Herpes simplex, but bacterial infections (commonly Mycoplasma) and fungal diseases are also implicated.
Erythema multiforme
Cutaneous larva migrans
Herpetic whitlow
Erythema nodosum 
Erythema nodosum
Ecthyma
Factitious dermatitis
Pityriasis rosea