Skin all over the body constantly sheds dead cells from the outer layer or epidermis. Dandruff refers to large, loose flakes of skin shed from the scalp, which can cling to the hair or fall onto the shoulders. The skin in those with dandruff is thought to shed more often than in those without it. The skin between the shafts of hair on the scalp is comparatively loose. Just beneath the surface, a mixture of yeast and bacteria often develops, particularly in those with oily skin. The number of yeast cells and bacteria are often higher in those with dandruff and many scientists believe that this combination is the actual cause of dandruff.