#Describe the symptoms of alopecia areata.# The disease begins either suddenly, without premonitory symptoms, one or several patches being formed in a few hours; or, and as is more usually the case, several days or weeks elapse before the bald area or areas are sufficiently large to become noticeable. The patches continue to extend peripherally for a variable period, and then remain stationary, or several gradually coalesce and form a large, irregular area involving the entire or a greater portion of the scalp. The skin of the affected regions is smooth, faintly pink or milky white, and at first presents no departure from the normal; sooner or later, however, the follicles become less prominent, and slight atrophy or thinning may occur, the bald plaques being slightly depressed. [Illustration: Fig. 38. Alopecia Areata--complete hair loss.] Occasionally, usually about the periphery and in the early stages, a few hair-stumps may be seen. #What course does alopecia areata pursue?# Almost invariably chronic. After the lapse of a variable period the patches cease to extend, the hairs at the margins of the bald areas being firmly fixed in the follicles; sooner or later a fine, colorless lanugo or down shows itself, which may continue to grow until it is about a half-inch or so in length and then drop out; or it may remain, become coarser and pigmented, and the parts resume their normal condition. Not infrequently, however, after growing for a time, the new hair falls out, and this may happen several times before the termination of the disease. #Are there any subjective symptoms in alopecia areata?# As a rule, not; but occasionally the appearance of the patches is preceded by severe headache, itching or burning, or other manifestations of disturbed innervation. #State the cause of alopecia areata.# The etiology is obscure. Two theories as to the cause of the disease exist: one of these regards it as parasitic, and the other considers it to be trophoneurotic. Doubtless both are right, as a study of the literature would indicate that there are, as regards etiology, really two varieties--the contagious and the non-contagious. In America examples of the contagious variety are uncommon. #Does the skin undergo any alterative or destructive changes?# Microscopical examination of the skin of the diseased area shows little or no alteration in its structure beyond slight thinning. #How do you distinguish alopecia areata from ringworm?# The plaques of alopecia areata are smooth, often completely devoid of hair, and free from scales; while those of ringworm show numerous broken hairs and stumps, desquamation, and usually symptoms of mild inflammatory action. In doubtful cases recourse should be had to the microscope. #What is the prognosis in alopecia areata?#