Dandruff is shedding or flaking of the skin on the scalp.  The most common causes of dandruff are eczema and seborrheic dermatitis.  The skin may be itchy and flakes may accumulate on the scalp, shedding onto the clothing.  Dandruff is not contagious however it is a chronic problem.  That means that while it can be controlled with shampoos and lotions, it cannot be cured and the symptoms may recur.