Dandruff is a condition characterized by excess scalp cells coming off in flakes, and can have many causes.
It may occur with either a dry or greasy scalp, and may be due to heredity, environment or diet.
On a dry scalp, it may be due to a diet deficient in protein. When on a greasy scalp, it may be due to the over-production of sebum or 'natural oil', producing flaking on the scalp. Dandruff is simply the skin which flakes off the scalp, but the shedding has been accelerated for some reason. This hair condition can spread to the face if it is not treated.
Acute dandruff (which can also result in hair loss) needs medical attention. Consult a trichologist (hair specialist) or your doctor. Ordinary mild dandruff can, however, be effectively treated with home remedies.
It is most essential to keep your hair clean. Your brush, comb, hair-pins etc. must be frequently washed or else you will re-infect your scalp each time you use them. Yes, dandruff is infectious. Remember never to borrow or lend your combs and brushes.