Dear Doctors: I have dandruff, and my doctor says it’s from seborrheic dermatitis. Can you explain what that is? I’ve been using the special shampoo I was given, and it helps. When I stop using it, though, the dandruff comes right back. Also, it’s making my hair really dry.
Dear Reader: Dandruff is a condition in which the skin on the scalp begins to flake and shed. It is often caused by a mild form of an inflammatory skin condition known as seborrheic dermatitis.
The word “seborrheic” refers to the sebaceous glands. These are miniscule glands embedded in the skin, almost always alongside a hair follicle. These glands secrete a waxy and oily substance known as sebum. The degree to which someone’s hair is naturally oily or dry is connected to the activity of their sebaceous glands.
When seborrheic dermatitis develops on the scalp, it is referred to as dandruff. It is not a danger to health, and it is not contagious. The most visible symptom of dandruff is the presence of the white flakes that you have described. These are dead skin cells, which become pale and translucent as they are shed. Additional symptoms can include itching on the scalp and areas of thickened, scaly or crusty skin.
Seborrheic dermatitis is often associated with an overgrowth of a genus of fungus known as Malassezia. It is a yeast that naturally occurs on the skin. This type of yeast requires fat for nourishment, which is why it is commonly found near the sebaceous glands. When something causes an overgrowth of the yeast, it can trigger an inflammatory response. Dry or cold weather can lead to flares of dandruff symptoms. So can hormonal shifts, a buildup of hairstyling products or the warm and humid microclimate created by wearing a hat or wig.
Treatment of seborrheic dermatitis on the scalp has two main targets. One is to reduce the colonization of the Malassezia yeast. The other is to manage any symptoms of inflammation that are making the person uncomfortable. When the sebaceous glands of the scalp are overactive, they produce an abundance of sebum. This, in turn, can encourage the growth of the Malassezia yeast associated with dandruff symptoms. When this occurs, modulating sebum production is also an important part of managing the condition.
The shampoo that you have been advised to use contains an antifungal agent that is designed to slow or stop the growth of the yeast. However, because it does not completely eradicate the yeast, ongoing use of the shampoo is necessary to manage the fungal infection. Because reducing sebum production is also one of the goals of treatment, these products can lead to dry hair, as you have experienced. Dandruff shampoos also contain ingredients to ease itchiness and reduce flaking. These shampoos come in a variety of formulas, with different added ingredients. With a bit of trial and error, you can find the brand of shampoo that works best for your specific situation. Some people find using a rotation of different products can be helpful.
(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)
