A group of spots or an area of red, inflamed skin. A rash is usually temporary and is only rarely a sign of a serious underlying problem. It may be accompanied by itching or fever. Rashes are classified according to whether they are localized (affecting a small area of skin) or generalized (covering the entire body), and the type of spots. A bullous rash has large blisters, a vesicular rash has small blisters, and a pustular one has pus-filled blisters. A macular rash consists of spots level with the surrounding skin and discernible from it by a difference in colour or texture. Nodular and papular rashes are composed of small, raised bumps. Rashes are the main sign of many infectious diseases (such as chickenpox), and are a feature of many skin disorders, such as eczema and psoriasis. They may also indicate an underlying medical problem, such as the rashes of scurvy or pellagra, which are caused by vitamin deficiency. The rashes of urticaria or contact dermatitis may be caused by an allergic reaction. Drug reactions, particularly to antibiotic drugs, are a common cause of rashes. A diagnosis is based on the appearance and distribution of the rash, the presence of any accompanying symptoms, and the possibility of allergy (for example, to drugs). Any underlying cause is treated if possible. An itching rash may be relieved by a lotion, such as calamine, or an antihistamine drug.


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