About hair loss. Hair loss may be either the result of illness or a normal genetic response to testosterone, the male sex hormone. A healthy human head has from 80,000 to 150,000 hairs, each of which passes through three phases of growth independently of all the others. At any time, 90 percent of the hairs are in the growing stage (anagen), which lasts anywhere from 1 to 5 years. Growth is followed by a resting phase (telogen); this ends after a few months, after which the hair is shed (catagen) to allow new growth. A daily loss of 50 to 200 hairs is a normal part of the cycle.
Although baldness is mediated by hormonal factors, it tends to run in families; your risk may be deduced from the number of bald males among members of both parents' families. Abnormal hair loss may be precipitated by metabolic disorders (including diabetes, thyroid disease, and crash diets); damage to hair shafts caused by harsh treatments; stress brought on by illness; hormonal changes of pregnancy; medical treatment, including cancer chemotherapy; and very severe scalp disorders.
Nutritional causes may be a grossly excessive intake of vitamin A or a deficiency of iron, biotin, zinc, or protein. Such deficiencies are rare, although an excessive intake of raw egg whites can lead to a depletion of biotin.
Treatments. The only medicines for baldness are minoxidil (Rogaine), a topical medicine, and finasteride (Propecia), an oral prescription drug. Hair loss due to stress or drug treatment is generally temporary. Hair that falls out during a crash diet soon regrows once nutrition returns to normal. Hair lost in patches usually grows back without treatment, but in some instances, corticosteroid injections may be needed.
About dandruff. Dandruff -- excessive scaling of the scalp -- affects more than 50 percent of the population. It may be due to stress or a chronic or recurrent skin disorder, such as seborrheic dermatitis, but the most likely cause is infection by Pytyrosporum ovale fungus. This fungus is found naturally on the scalp but some people are more affected by it than others. It feeds on the skin's natural oils and causes irritation and shedding of dead skin. Many people shed flakes of dandruff, especially in winter, when the scalp may be dry. But some people have a hereditary tendency to develop skin problems that are triggered by a sensitivity to specific foods. Because the offending food varies from one person to the next, the only reasonable advice is to avoid foods that seem to make dandruff worse.
Treatments. Some cases of dandruff may respond to flaxseed oil, which seems to help itchy skin conditions such as psoriasis and eczema. Take 1 to 2 teaspoons a day. You'll need to wait several weeks or months to see an effect.
