The chapter describes about the connective tissue diseases and drug eruptions. A range of connective tissue diseases are discussed in the chapter, including lupus erythematosus, dermatomyositis, and scleroderma. Some of the reactive skin diseases explained in the chapter include erythema multiforme, Stevens-Johnson syndrome, fixed drug eruption, DRESS (drug rash with eosinophilia and systemic symptoms) syndrome, drug induced pigmentation, drug induced nail pigmentation, and erythema nodosum. Erythema multiforme is a self-limited, recurrent disease with each episode lasting 1–4 weeks; it shows the classic target lesion with three zones—central dusky purpura, an edematous, pale middle zone, and peripheral erythema. The central area may be bullous.