Dandruff (also called scurf and historically termed Pityriasis capitis) is due to the excessive shedding of dead skin cells from the scalp. As it is normal for skin cells to die and flake off, a small amount of flaking is normal and in fact quite common. Some people, however, either chronically or as a result of certain triggers, experience an unusually large amount of flaking, which can also be accompanied by redness and irritation.

Most cases of dandruff can be easily treated with specialized shampoos.
Excessive flaking can also be a symptom of seborrhoeic dermatitis, psoriasis, fungal infection or excoriation associated with infestation of head lice.
Dandruff is a global phenomenon and many people find that dandruff can cause social or self-esteem problems. Treatment may be important purely for psychological reasons.

Caring for Dandruff
Shampooing frequently to wash away flakes before they build up is the first step to treating dandruff. Surprisingly dandruff shampoos typically treat the excess shedding and scalp fungus rather than the dry, scaly skin. I recommend using a conditioner after rinsing the dandruff shampoo, because I find that dandruff treatments can further dry hair and the scalp.
Be patient. While anti-dandruff shampoos may produce results after a few uses, it can take a week or two to see the difference.

Dietary changes for Dandruff
Eat a healthy, balanced diet. As if you needed another reason to eat right, it turns out that a healthy diet may ward off the flakes. Make sure to get plenty of zinc, Omega-3 fatty acids, and B-vitamin, and avoid excessive yeast and sugar. Research suggests that dandruff is at least in part caused by a fungus that thrives in yeasty, fatty, sugary environments. Though this does not necessarily directly affect the conditions of your skin, your overall health will help with how your body responds to the fungus causing the dandruff.