Seborrheic Dermatitis and Psoriasis: What's the Difference?

Medically Reviewed by Debra Jaliman, MD on May 27, 2023
4 min read

Psoriasis has many imitators, but one that comes very close is seborrheic dermatitis. That’s because both conditions can cause red, scaly, inflamed patches on your skin.

To tell the two apart, you’ll need to take a close look at the differences in those patches, or plaques. Psoriasis starts as rough, red, scaly skin and grows into thick, usually silver-colored scales on top of those areas. These patches often show up on the scalp. You can also get them on your torso, limbs, hands, and feet.

Seborrheic dermatitis patches are more likely to vary in color. They may look whitish-yellow, red, or brown. They also tend to feel greasy or oily (the condition gets its name from the sebaceous, or oily, glands in the skin). This form of dermatitis, or inflammation of the skin, strikes most often on the scalp, on oily parts of the face (like the folds around the nose or in the ears and eyebrows), and on the upper chest and back. Think of it as dandruff 2.0. Simple dandruff causes only flakes, no inflammation, and it’s only on the scalp.

It’s tricky to figure out which condition is which when the flaky red patches are only on the scalp, with no other clues. It’s also possible to have both conditions at the same time. That’s called sebopsoriasis, and it can leave you with white and silver flakes.

The similarities. Seborrheic dermatitis and psoriasis tend to be lifelong conditions. They can take an emotional toll too, especially when the patches are very noticeable. Both can often be managed. Psoriasis usually needs stronger medicines than seborrheic dermatitis.

Both can also flare. This happens when you’re exposed to certain triggers that are unique to you, like the weather or stress.

Neither condition is contagious. You can’t pass it to someone or get it from someone. But both conditions can run in families. So having one (or both) can be in your genes.

The differences. Psoriasis is an autoimmune disease. That means your immune system is sending out faulty messages, and your body responds by growing skin cells too quickly.

Psoriasis plaques are itchy like seborrheic dermatitis, but they can also be painful. About one-third of people with psoriasis get a form of arthritis as the disease gets worse.

The scales on psoriasis plaques are thicker than those of seborrheic dermatitis, with more defined edges. Their color is closer to silver than the white or yellow of seborrheic dermatitis scales.

The exact cause of seborrheic dermatitis isn’t clear, but it’s probably the result of things like:

  • Too much Malassezia, a common yeast found on everybody’s skin
  • Too many androgens, a group of common hormones
  • Too much oil production
  • A family history of dermatitis
  • A personal history of psoriasis, acne, or rosacea (among other skin conditions)

It’s also hard to pinpoint exactly why someone gets psoriasis. As with other autoimmune diseases, it’s probably a combination of the genes you’re born with and things in the world around you that trigger the disease. Those triggers include infections, an injury to the skin, smoking, drinking, and even stress.

In general, seborrheic dermatitis symptoms include itchiness, red or inflamed skin, and flaking. But they can vary based on where the dermatitis happens:

  • On the scalp: itchy white scales that flake off (in babies, the scales are more yellow)
  • On the sides of the face and along the edges of eyelids: pink-to-red patches with scales
  • On cheeks: inflamed hair follicles
  • On the chest and along the hairline: flaky patches in oval or ring shapes
  • In body folds and creases: red skin

Psoriasis varies from person to person. It can cause small patches or widespread areas. Typical symptoms include:

  • Red areas of skin, often covered by thick scales
  • Cracks in the skin that may bleed
  • Itching
  • Burning

Psoriasis can also affect your nails. They may become thicker and get pits or ridges. If you get psoriatic arthritis, joints will feel stiff and look swollen.

Doctors use some of the same steps to diagnose many skin conditions, including these two. They will ask about your health and examine your skin and scalp and any other affected areas. They might take a small sample of skin to be checked under a microscope. This can help rule out other conditions. If it is psoriasis, it’ll help determine which type you have.

It can be hard to tell scalp-only psoriasis from seborrheic dermatitis. Newer, higher-powered microscopes can show differences in the shapes of the scales. Watching for changes in skin tissue can also help pinpoint which condition is which.

If you have a rash that isn’t going away or is getting worse, call your doctor to get the right diagnosis and treatment. Though the conditions are somewhat similar, what works for one may not help the other. This is especially true for severe psoriasis.