rash(redirected from butterfly rash)
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an eruption on the skin or mucous membrane of man, the cause of which can be either external and internal. Rashes accompany skin and other types of diseases. The external causes can be physical or chemical, while internal causes include diseases of the nervous and hemopoietic systems, metabolic disorders and functional disorders of certain organs (digestion, endocrine glands), infectious diseases (measles, scarlet fever), and allergic reactions (urticaria). Rashes may be primary or secondary. Primary rashes appear on previously normal skin or mucous membrane (spots, wheals, vesicles, pustules, tubercles). Secondary rashes appear as a further development of primary elements (pigmentation, scales, crusts, abrasions, ulcers, fissures, scars). The location, number, combination, color, shape, depth, and duration of the eruptions are helpful in diagnosing the disease.