Dandruff is the shedding of dry white flakes of dead skin, as the top layer (epidermis) of the skin constantly replaces itself and cells are pushed outward, where they eventually die and flake off, which leaves the scalp dry and itchy. Some common causes for dandruff are: Dry Skin Irritated and oily skin (seborrheic dermatitis) Unclean and unhealthy habits. Over use or sensitivity to Hair products Infrequent washing or shampooing It is common among most of the people and the severity may fluctuate with season, as it often worsens in winter. Emotional stress may also aggravate the severity of dandruff. If dandruff is worsening (spreading, causing hair loss, increasing redness, painful, infected) despite proper skin care and hair hygiene, seek for a medical assistance to prevent further aggravation.