What is the science behind dandruff? What happens to the skin in dandruff?
All human skin is in a constant state of renewal, whether we have dandruff or not. Skin cells are constantly produced at the bottom of the epidermis (the uppermost layer of the skin) and push towards the skin’s surface. The skin that is visible to us is composed of old dead cells. Thus, the skin is in a constant state of renewal. Shedding of the skin is a normal part of the skin’s life cycle, whether on the scalp or other parts of the body. Even though we shed as many as a million skin cells a day, they are usually too small to be visible.
In dandruff, the skin turnover accelerates as much as ten times the usual rate. With accelerated shedding, skin cells pile on top of each other, producing large visible clumps of oily skin on the scalp. It is thought that a fungus called Malassezia plays a role in dandruff. Oleic acid, a byproduct of sebum when metabolized by the fungus, is believed to cause inflammation in the scalp, leading to accelerated skin shedding and dandruff.
- Skin is constantly renewed. As new skin cells continually push towards the surface, old cells are shed.
- Normally skin shedding is not visible to the naked eye as the pieces of skin are too small. Under normal circumstances, a skin takes approximately 30 days from the time it is produced at the bottom of the epidermis until it sheds at the surface.
- In dandruff, skin production accelerates as much as ten times the usual rate causing it to clump at the surface into visible pieces. This acceleration is generally caused by inflammation.
- Malassezia, which naturally resides on the human scalp, is thought to play a significant role in dandruff. When it feeds on sebum, a natural oil produced in the skin, it releases an oil that is thought to cause inflammation of the scalp, causing dandruff.
How do dandruff shampoos treat dandruff?
Although numerous active ingredients help treat dandruff, and many more individual products, all dandruff shampoos attack the problem of dandruff in one of three general ways:
- Keratolyics such as salicylic acid help the surface skin loosen and shed away easier. These agents help separate the clumps of skin seen in dandruff.
- Antifungal agents such as zinc pyrithione or ketoconazole reduce the number of Malassezia yeasts responsible for dandruff proliferation.
- Steroidal agents help reduce inflammation in the skin and thus, reduce the acceleration of skin production.
