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blackhead, yellowish or blackish plug of material accumulated in the duct of a sebaceous gland. The material consists of keratin (horny cells of the epidermis) and modified sebum (oily secretions of the sebaceous gland). Blackheads are the primary lesions in acne. Treatment is the same as for acne, with frequent cleansing of the skin followed by the application of astringent solutions. Plugs should be extracted only by a physician, since damage to the surrounding tissues occasioned by squeezing often leads to scarring.
Blackheath, common, 267 acres (108 hectares) in Lewisham and Greenwich boroughs, London, England. It was the gathering place of highwaymen and of several martial groups, including the followers of Wat Tyler in 1381 and of Jack Cade in 1450, who made Blackheath the headquarters for their attacks on London.
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a residential district in SE London, mainly in the boroughs of Lewisham and Greenwich: a large heath formerly notorious for highwaymen
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005