What is seborrheic dermatitis?
Seborrheic dermatitis is a common skin disease. It looks like yellow, greasy scales on top of pink or red irritated skin in light-skinned people or lighter (white) patches in dark-skinned people. It can be itchy or burn.
The rash can appear anywhere on the body that has a lot of oil glands, such as the scalp, face, ears, chest, stomach, or groin. When seborrheic dermatitis is on your head, it causes dandruff.
You tend to grow fungus in these oily areas naturally. In some people, the mix of too much fungi (overgrowth) and too much oil (sebum) triggers this rash.
Seborrheic dermatitis is common in infants and adults. Luckily, it’s easy to treat with prescription creams and shampoos.
It is rare that the rash is a sign of a different underlying problem.
Most common symptoms
I often look at the elbows and knees and the fingernails to differentiate seborrheic dermatitis from psoriasis. If there are pimples on the forehead and cheeks in combination with dilated blood vessels, then it is more likely rosacea. —Dr. Lauren Levy
Seborrheic dermatitis mostly affects adults and infants (under 1 year old).
The most common symptom is a red or pink rash with greasy, yellow scales. Sometimes when on the scalp, it may just cause widespread flaking without redness.
In babies, it’s usually on the scalp and is called “cradle cap.” In adults, the rash might be anywhere on the body that produces oil or in between skin folds—like the scalp, face, ears, chest, stomach, and groin.
Sometimes the rash looks like psoriasis. But psoriasis usually appears on the outer elbows as well. Psoriasis scales are also drier and more silver in color.
Seborrheic dermatitis can also be confused with rosacea in adults. Especially if it’s on the face. But rosacea causes more redness, visible blood vessels, and pimples, but not scales.
In infants, seborrheic dermatitis can look like atopic dermatitis (eczema), but eczema is very itchy and usually does not occur in the diaper area.
- Rash with greasy scales on the scalp, face, ears, chest, and body folds.
- The skin under the scales may be red in light-skinner people or white in dark-skinned people.
- The rash might itch or burn.
What is the best treatment for seborrheic dermatitis?
Most patients think that the rash is contagious—it's not! The good news is that it cannot be spread from one person to another. —Dr. Levy
For mild cases, an over-the-counter dandruff shampoo may work. If not, call your doctor. They might prescribe a medicated cream or shampoo. Your doctor might also send you to a skin specialist (dermatologist), who will examine your whole body for rashes and prescribe medications.
Seborrheic dermatitis is easily treated with topical (applied to the skin) medications. This includes over-the-counter or prescription antifungal or corticosteroid creams that you apply directly on the rash/scales.
- Zinc pyrithione is the main ingredient in many over-the-counter anti-dandruff shampoos. It kills fungus and can relieve the flaking and itch of dandruff. When using the shampoo, apply it to the scalp and leave on for several minutes before rinsing out. You can use it daily or several times a week.
- Ketoconazole is the main prescription antifungal medication used. It comes in two forms: a skin cream or a shampoo. The cream can be used directly on the face and body wherever you have the rash. The shampoo should be lathered up and left on the scalp for 5 minutes before rinsing. It should be used daily until the rash is gone, and then can be used several times a week to prevent it from returning.
- Low-potency topical steroids: These are prescribed by a doctor and can make your skin less irritated by calming down inflammation. Use it until your symptoms are better, and stop once they’re under control.
Seborrheic dermatitis in infants
Seborrheic dermatitis typically occurs on the scalps of infants. It is very common. Just washing the scalp regularly with mild shampoo helps loosen the scales. A soft toothbrush can also be used to remove the scale.
Unlike with adults, the rash and scales should go away within several months. If it doesn’t, make an appointment with a pediatrician. Your baby might need a medicated shampoo, such as ketoconazole.
There are no clear risk factors for seborrheic dermatitis, though genetics may play a role.
People with certain illnesses are more likely to have it, such as those with HIV or AIDS and people with Parkinson’s disease. Parkinson’s causes your body to make more oil (sebum).
Causes of seborrheic dermatitis
Your skin makes sebum, and some areas have a lot of oil glands, like the scalp, face, and chest. There is also fungi that live on your skin, especially in oily areas.
The fungi break down the sebum. Sometimes that broken-down sebum can trigger your immune system to respond which causes your skin to get red and inflamed. That in turn leads to the yellow scales, which contain sebum and skin cells. That’s why seborrheic dermatitis looks greasy.
It is not an infection—everyone has the fungi on the skin that cause this rash. Some people have more of this fungi and more oil in their skin, which makes the rash come out. Others have a strong immune reaction to the fungi, which makes the rash come out. Nothing you did caused this rash. —Dr. Levy
To prevent seborrheic dermatitis from coming back, use the medicated cream or shampoo occasionally, even after the rash is gone. This is called maintenance therapy. Ask your doctor how often you should use the medication.
Dr. Bae is a native Californian who obtained his BA in Molecular and Cell Biology from the University of California, Berkeley and obtained his MD from Boston University School of Medicine. He is currently training in Dermatology as a resident physician at Brown University / Rhode Island Hospital.
When he's not in clinic he enjoys cooking, tennis, weight lifting and strategic board games.