Dandruff occurs when the scalp sheds dead epidermal (skin)
cells in large clumps. Dandruff scales appear dry, white or
grayish, appearing as small, unsightly patches, especially on top
of the head.
Scalp cells replenish themselves in a pattern similar to that
of hair, but more rapidly: The skin of the head renews itself about
once a month. Dead scalp cells are constantly being pushed from the
deepest layer of the epidermis to the skin's surface, where they
gradually die. Usually the scalp sheds them in a nearly invisible
way. But for reasons that are still unclear, cell turnover
sometimes becomes unusually rapid, and dead cells are shed as the
visible flakes called dandruff.
Although most people assume dandruff comes from a dry scalp,
the opposite is true: People with oily scalps tend to suffer most
from dandruff.
Children under 10 rarely have dandruff, but it is common in
adolescents.
Dandruff is treatable with over-the-counter (OTC) products and
causes no general health problems or permanent damage. But care
must be taken not to confuse simple dandruff with other conditions
that also cause flaking of the scalp, such as seborrheic dermatitis
or psoriasis.