Temporary Conditions
Dandruff, or dry, flaky scalp, can be caused by a number of things. The most common cause of dandruff is dry skin, which can affect the scalp just as any other area of the body. Dry skin is most common during the winter because the air is cold, which chaps the skin. Heating systems pump out hot, dry air to further dry out the scalp. Another common cause of dandruff is infrequent shampooing or hair washing. According to womenfitness.net, if the hair is not cleaned at least twice a week, then skin cells and oil can accumulate on the scalp. The oil accumulation can cause the skin to dry out and flake, which will be exacerbated by the dead skin cells on the scalp.
Skin Conditions
There are several skin conditions that can also lead to dandruff, including eczema. Eczema causes itchy skin eruptions and can affect the scalp, where it can cause the skin to dry and flake off. Though the exact cause of eczema is not known, it is thought to be caused by a combination of dry air and a problem in the immune system. Another condition that can cause dandruff is psoriasis. Psoriasis is caused by an abnormally fast buildup of cells on the skin's surface. Psoriasis causes the formation of silvery scales of skin as well as raised red patches that can be painful. When psoriasis affects the scalp, the silvery scales can fall off, leading to dandruff.
Other Causes
One common cause of dandruff is seborrheic dermatitis. This condition is marked by oily, irritated skin that is often covered with yellow or white scales that flake off. Dandruff also can be caused by a reaction to a hair care product. Dandruff that suddenly appears after you use a new hair product should raise suspicion that it is caused by sensitivity of the scalp to that product. A type of fungus called malassezia can cause dandruff. This fungus normally grows on people's scalps but it can get out of hand, leading to the scalp becoming irritated. This skin irritation will lead to dandruff.
