Dandruff is those pesky white flakes you sometimes see on your scalp and shoulders. It's a common condition that can be caused by a few things. Often, it's due to a dry scalp or a skin condition called seborrheic dermatitis. It can also be triggered by not shampooing enough, which leads to a buildup of oil and skin cells. Sometimes, a yeast-like fungus called Malassezia can also be a culprit.