Canities(redirected from canities unguium)
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the irreversible change in hair color to silvery white owing to the disappearance of pigment and the appearance of air bubbles in the hairs. Canities generally starts on the head and then spreads to the moustache, beard, and pubic region. Physiological canities starts between the ages of 35 and 40, with brunets graying sooner than blonds. Premature canities may start at the age of 20 and even earlier. Premature canities may be hereditary or may be caused by shock, disorders of the endocrine glands (thyrotoxicosis, diabetes mellitus), infectious diseases (typhoid), anemia, and hypovitaminoses. The hair of persons suffering from alopecia areata and erysipelas may temporarily turn gray. Canities may also afflict persons who have taken certain drugs for a long time. Cosmetic preparations, including dyes, are used to restore the original color of the hair.