What causes dandruff?

Hello JenM

Thank you for writing!

Approximately 50 million Americans of all ages and walks of life suffer from dandruff. Although it poses no real health danger, Americans spend $300 million per year to control the annoying white flakes.

We all know dandruff when we see it. How annoying is it to keep brushing off those unsightly snowflakes that accumulate on your hair, shoulders, and clothing!

Despite what television advertisements might have you believe, dandruff is simply an overabundance of a natural process that occurs in everyone.

Throughout our lives, the skin cells covering our bodies are constantly "dying" and being replaced by new skin cells. When old skin cells die, they dry up and fall away, or "shed." Generally, this continuing process occurs at a slow enough pace so as to remain invisible.

Dandruff occurs as this process is accelerated. In most people, the skin over the entire scalp replaces itself approximately once a month. At this pace, the process remains invisible as long as you wash your hair and scalp regularly (at least 2-3 times per week).

In some people however, this replacement of old skin cells speeds up, making it more difficult to keep up with the pace. When the process accelerates to every 10-15 days, visible dandruff occurs. If it accelerates further (to every five days or less), severe dandruff results.

In most instances, a mild case of dandruff is likely just an outgrowth of dry scalp skin. However, in more severe cases of dandruff, the culprit is seborrheic dermatitis, a skin condition that, in addition to causing an itchy, scaly rash, also accelerates the process of shedding and replacing old, dead skin cells. Though most often found on your scalp, seborrheic dermatitis can also occur elsewhere on the body, usually on the eyebrows, eyelids, nose, around the ears, or on the chest.

What causes seborrheic dermatitis? It's not known for sure. However, it appears that Pityrosporum ovalae, a naturally occurring, yeast-like organism present in all human skin plays a significant role. Minor immune abnormalities and changes in skin secretions are also implicated.

Because it results from a naturally occurring process, dandruff cannot be cured. However, it can be controlled. The first step is to simply increase the rate at which dead skin cells are removed from the scalp.

In mild cases of dandruff, this can be accomplished by washing your hair more frequently—for example, every day rather than every two or three days. In moderate, and in some more severe cases, the increased frequency of shampooing must be combined with the use of medicated, over-the-counter dandruff shampoos.

Shampooing Techniques

Whether using a regular or anti-dandruff shampoo, a specific shampooing regimen should be followed to help control dandruff.

Massage the scalp with the shampoo to loosen flakes.
Let the shampoo lather remain in your hair and on the scalp for 3-5 minutes (or, in more severe cases, 15-30 minutes) before rinsing it out.
Rinse your hair and scalp thoroughly to remove as much of the dry, dead skin as possible.

Over-the-Counter Medicated Shampoos -

These anti-dandruff shampoos are thought to help control dandruff by:

Pulling the dead skin cells away from the scalp so they can be rinsed away.
Killing the Pityrosporum ovalae organisms on the scalp and slowing down the process of shedding and replacing dead skin cells.
Decreasing the rate of scalp skin turnover.
To accomplish this, anti-dandruff shampoos use any one of a number of dandruff-fighting ingredients approved by the US Food and Drug Administration, including:

Products containing salicylic acid (Sebulex) and coal-tar (Tegrin), which help remove dead skin cells from the scalp and/or slow down the rate at which these cells are created. In some folks, however, salicylic acid, due to its "harsh" nature, may actually increase the rate at which dead skin cells are created.
Products containing zinc pyrithione (Head and Shoulders), which kill pityrospora.
Products containing selenium sulfide (Selsun Blue), which slow down the creation of dead skin cells and kill pityrospora.

Natural Products-

One small double-blind study found benefit in fighting dandruff with an extract made from the traditional Mexican herb Solanum chrysotrichum. Shampoo made with oil from the Australian tea tree have also shown promise, as has aloe vera.

Since different people tend to have success with different products, experiment with several anti-dandruff shampoos until you find one that works for you.

When Over-the-Counter Products Don't Work
If your dandruff is severe and/or seborrheic dermatitis has affected other areas of your body in addition to your scalp, you should see a dermatologist. He or she can evaluate the condition and prescribe one of a number of stronger treatments, which include:

Prescription-strength anti-dandruff shampoos that contain ketoconazole, an antibacterial ingredient that is stronger than zinc pyrithione
Prescription-strength salicylic acid or prescription strength coal-tar, which comes in a lotion that is applied to the skin and left on for a number of hours
Prescription-strength steroid preparations that are applied to the skin

I know this is a lot of information but I hope it helps!

Best,
Susan