Dandruff, Seborrheic Dermatitis,
or Scalp Psoriasis?

A flaky, itchy scalp almost always comes from one of three conditions. Dandruff is mild flaking without much redness and responds to an over-the-counter antifungal shampoo. Seborrheic dermatitis is dandruff’s more inflamed form: greasy yellow flakes on red patches, often also on the eyebrows, sides of the nose, and behind the ears. Scalp psoriasis causes thick, silvery, sharply outlined plaques that often extend past the hairline, and it needs prescription treatment. All three are treatable, none is contagious, and none is caused by poor hygiene. A dermatologist can tell them apart at a glance and, when needed, treat scalp problems at both Belaray offices.

Why Does the Scalp Flake?

The scalp has the densest oil glands on the body and a resident yeast, Malassezia, that feeds on that oil. In some people the yeast and its by-products irritate the skin, speeding up cell turnover so that dead cells shed in visible clumps. That is dandruff, and when inflammation joins in, seborrheic dermatitis. Scalp psoriasis is a different process: an autoimmune signal that drives skin cells to mature in days instead of weeks, piling up into thick scale. Other causes of a flaky or itchy scalp include contact dermatitis from hair products, scalp eczema, fungal infection (tinea capitis, mostly in children), and scalp folliculitis, which a dermatologist will also consider.

Dandruff vs. Seborrheic Dermatitis vs. Scalp Psoriasis

What Is Dandruff?

Dandruff is the mildest and most common of the three, affecting about half of adults at some point. The flakes are small and white or gray, there is little redness, and the itch is mild. It is a scalp-only condition. Dandruff is the mild end of the seborrheic dermatitis spectrum, which is why the same antifungal shampoos treat both.

What Is Seborrheic Dermatitis?

Seborrheic dermatitis is an inflammatory condition driven by Malassezia yeast and the skin’s reaction to it. On the scalp it produces greasy, yellowish flakes stuck to pink or red patches. It also appears where oil glands are dense: the eyebrows, the creases beside the nose, the ears and behind them, the beard, the center of the chest, and in babies as “cradle cap.” It flares with stress, cold dry weather, illness, and fatigue, and it tends to come and go for years. It is more common and more severe in people with Parkinson’s disease, HIV, and some neurological conditions.

What Is Scalp Psoriasis?

About half of people with psoriasis have it on the scalp, and for some it is the only site. The plaques are thick, red, and raised with silvery-white scale that is drier than the greasy flakes of seborrheic dermatitis, and they are sharply outlined. A key clue is that scalp psoriasis commonly extends beyond the hairline onto the forehead, the back of the neck, and the skin around the ears. Look for psoriasis elsewhere: the elbows, knees, lower back, navel, and nails. Scratching or picking thick plaques can cause temporary hair loss, which regrows once the plaques are treated. See our guides to psoriasis treatment and eczema vs. psoriasis.

How Are Scalp Conditions Treated?

Dandruff and Mild Seborrheic Dermatitis

• Antifungal shampoos with ketoconazole 1 percent, zinc pyrithione, selenium sulfide, or ciclopirox (prescription). Lather, leave on for five minutes, then rinse; use two to three times a week and rotate between two active ingredients if one stops working.
• Salicylic acid or coal tar shampoos to loosen flakes.
• Continue once a week after clearing, because the yeast returns when the shampoo stops.

Moderate to Severe Seborrheic Dermatitis

• Prescription-strength ketoconazole 2 percent or ciclopirox shampoo.
• A short course of a topical corticosteroid solution, foam, or oil for the scalp, and a mild steroid or a calcineurin inhibitor (tacrolimus, pimecrolimus) for the face, where strong steroids are avoided.
• Roflumilast foam, a newer steroid-free prescription for seborrheic dermatitis of the scalp and body, approved for ages 9 and up.

Scalp Psoriasis

• Scale removal first: salicylic acid shampoos or oils soften thick scale so medication can reach the skin.
• Topical corticosteroid solutions, foams, sprays, or shampoos (clobetasol shampoo is designed for the scalp), often combined with a vitamin D analogue such as calcipotriene.
• Tar shampoos for maintenance.
• For severe or widespread scalp psoriasis, or psoriasis elsewhere on the body: narrowband UVB phototherapy, offered at Belaray, or systemic medications including biologics, which clear the scalp in most patients.

Scalp Care Tips for Any Flaking

• Shampoo regularly; letting oil build up feeds the yeast. For textured or dry hair that is washed less often, use the medicated shampoo on wash days and leave it on the scalp for five minutes.
• Apply medicated shampoo to the scalp, not just the hair, and rinse with lukewarm water.
• Do not pick or scrape scale; it causes bleeding, infection, and hair loss.
• Stop products that burn or sting. A new rash at the hairline after a new product may be contact dermatitis; see contact dermatitis and patch testing.
• Sunscreen the part line and any exposed scalp, especially where hair is thin.

When Should I See a Dermatologist?

• Flaking that has not improved after four weeks of an over-the-counter antifungal shampoo.
• Thick plaques, redness that extends past the hairline, or scale on the elbows, knees, or nails, which suggest psoriasis.
• Hair loss along with scalp symptoms. See hair loss: causes and treatment.
• Pain, pustules, oozing, or a tender boggy area, which can mean infection.
• Scalp flaking in a child with patchy hair loss, which may be a fungal infection needing oral medication.

Frequently Asked Questions

How can I tell if I have dandruff or psoriasis?

Dandruff produces small white or gray flakes with little or no redness and stays on the scalp. Scalp psoriasis produces thick, silvery-white scale on red, raised, sharply outlined plaques that often extend past the hairline onto the forehead, neck, or around the ears, and it is frequently accompanied by psoriasis on the elbows, knees, lower back, or nails. If an antifungal shampoo has not helped after four weeks, see a dermatologist.

Is seborrheic dermatitis the same as dandruff?

They are the same condition at different levels of severity. Dandruff is the mild end: flakes without much inflammation. Seborrheic dermatitis adds redness and greasy yellow scale, and it can also affect the eyebrows, the sides of the nose, the ears, the beard, and the chest. Both are driven by Malassezia yeast and respond to antifungal shampoos, with seborrheic dermatitis often needing a prescription as well.

What is the best shampoo for a flaky scalp?

For dandruff and mild seborrheic dermatitis, an antifungal shampoo containing ketoconazole, zinc pyrithione, or selenium sulfide, left on the scalp for five minutes two to three times a week. Rotate between two active ingredients if one stops working. For scalp psoriasis, a salicylic acid shampoo to lift scale followed by a prescription steroid shampoo or solution works better than antifungal shampoo alone.

Can scalp psoriasis cause hair loss?

It can, but the loss is usually temporary. Thick plaques, scratching, and picking can cause hair to shed in the affected areas, and hair regrows once the psoriasis is treated. Psoriasis does not scar the follicles. Persistent hair loss with scalp symptoms should be evaluated, because other conditions such as scarring alopecia can look similar.

Is seborrheic dermatitis contagious?

No. Seborrheic dermatitis, dandruff, and scalp psoriasis cannot be passed from person to person. Seborrheic dermatitis involves a yeast that lives on everyone’s skin; the difference is in how an individual’s skin reacts to it. The only common contagious scalp condition is tinea capitis, a fungal infection seen mostly in children, which causes scaly patches with broken hairs.

Why does my scalp get worse in winter?

Cold, dry air and indoor heating dry the scalp, and stress and illness in winter trigger flares of seborrheic dermatitis. Many people also wash their hair less often in cold weather, which lets oil build up and feeds the yeast. Keeping up with medicated shampoo once or twice a week through the winter prevents most flares.

Does cradle cap in babies need treatment?

Usually not. Cradle cap is seborrheic dermatitis in infants and typically clears on its own by 6 to 12 months. Softening the scale with a little baby oil or petroleum jelly, gently brushing it loose, and shampooing helps. If the rash is red, spreading to the face or diaper area, or not improving, a pediatric dermatologist can prescribe a mild treatment. See our guide to pediatric dermatology.

Related reading: psoriasis treatment, eczema vs. psoriasis, hair loss, pediatric dermatology, and the patient education hub.