causes include excessive use of hair sprays and gels, improper use of hair-coloring products, cold weather and dry indoor heating, infrequent shampooing of the hair or inadequate rinsing of the scalp and hair and fungal infections.
Eat a healthy diet. You can also take vit B6 and vit A and E which are good for hair and skin. Try medicated shampoos for dandruff
. There are a number of over-the-counter shampoos available that can help. The most effective ingredients -- antimicrobials -- to look for are zinc pyridinethione, selenium