Dandruff: What is it and how it should be treated?

As anyone who has dandruff knows, it can be embarrassing to wear black tops when they get covered in unsightly white flecks.  Fortunately, effective treatment for dandruff, a type of seborrheic dermatitis, exists.

What is dandruff?

Dandruff is a form of seborrheic dermatitis.  Seborrheic dermatitis is a common type of chronic dermatosis that usually affects areas of the body that contain plenty of sebaceous glands like the scalp, face, chest and body folds.

Sebaceous glands secrete sebum, a waxy substance which lubricates hair and skin.  Mild seborrheic dermatitis that affects the scalp is called dandruff (pityriasis sicca) and results in a characteristic flaking.  Of note, in infants, mild seborrheic dermatitis results in a condition called "cradle cap."

Dandruff can begin in childhood and has gradual onset.  The course of dandruff waxes and wanes with flare-ups and remissions common.  Infantile and adolescent dandruff and seborrheic dermatitis can remit with age or continue through adulthood. 

Dandruff and seborrheic dermatitis affects about 2 to 5 percent of the general population and is more likely to affect men.  Some people complain that their dandruff worsens during the fall and winter or in dry environments.  Moreover, sunlight has a variable effect on dandruff; some people think that sunlight improves their dandruff, and others think sunlight makes their dandruff worse.

Scaling typical of dandruff usually affects the entire scalp and can also affect eyebrows and eyelashes.

This scaling is usually gray-white or orange-red in color and sloughs off of either flattened lesions (macules or patches) or raised lesions (papules).  (The term :"lesion" is medical jargonese for irregular growths of skin.)  In addition to scaling, dandruff can also be dry and itchy, and inflammation is evident on histologic or microscopic examination.

What causes dandruff?

Some experts suggest that dandruff and, more generally, seborrheic dermatitis are caused by genetic predisposition to a "seborrheic state."  This seborrheic state may also be linked to a "prepsoriasis state."  In fact, many people with dandruff also have psoriasis on their trunks.  (Psoriasis typically presents with silvery scales.)  Comorbid presentation of seborrhea and psoriasis is so common that some have proposed the term "seborrhiasis."

In addition to genetics, the fungus M. furfur may play a role in the development of both soborrhea and psoriasis.

Dandruff and seborrheic dermatitis commonly present with the following conditions:

• Parkinson's disease;
• immunocompromised states like HIV and AIDS and cardiac transplant;
• nutritional deficiencies of zinc, niacin and pyridoxine.

Of note, facial paralysis secondary to Parkinson's disease or other conditions may play a role in the development of dandruff.

How is dandruff treated?

As you may be aware, shampoos are often used to treat dandruff.  These shampoos are often available over the counter (think T/Gel).  Prescription shampoos like Nizoral, which contains 2 percent ketoconazole, also works well.  The reason why an antifungal medication like ketoconazole may work well is because, as previously mentioned, dandruff may have a fungal underpinning.

When using a shampoo to treat dandruff, you should first wet your hair before application and then thoroughly rinse your hair after application.  Don't leave shampoo in your hair after showering. Additionally, you can also apply glucocorticoid (steroid) gels, lotions or solutions after using a tar or ketaconazole shampoo to help alleviate symptoms like itchiness.  Other creams including tacrolimus, pimecrolium and hydrocorisone may also help relieve the discomfort of dandruff.

With severe cases of dandruff and seborrheic dermatits, 13-cis-retinoic acid or retinoic acid can be taken orally and is highly effective.  Retinoic acid or retinol ia a derivative of vitamin A and is commonly used to treat acne.  Women who are pregnant or planning to become pregnant should not take retinoic acid because this drug is a teratogen and will hurt the fetus.  If you do decide to take retinoic acid for dandruff and seborrheic dermatits, please be sure to use contraception, too.

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