If your scalp is itchy and your shoulders are often covered with a snowfall of flakes, you’ve probably wondered at some point, is this just dandruff — or could it be scalp psoriasis? It's true that both conditions can cause those annoying white flakes, but dandruff and scalp psoriasis spring from different causes and warrant different treatments. Here to help sort out all the differences is dermatologist Mona Gohara, M.D., associate clinical professor of dermatology at Yale School of Medicine.
What is dandruff? The causes and symptoms
Dandruff is a very common condition of the scalp that results in dry skin flakes, which end up caught in a person’s hair or on their clothes. According to the American Academy of Dermatology (AAD), it generally doesn’t require medical treatment, but it can be itchy and uncomfortable, as well as embarrassing to those having to deal with it. Here are the causes:
• A yeast imbalance. “There’s a type of yeast in all of our bodies called malassezia, part of our body’s normal microbiome,” says Dr. Gohara. “Dandruff, or seborrhea, is caused by an overgrowth of that.”
• An oily scalp. Dandruff can also be associated with increased oil production of the scalp, says Dr. Gohara, evidenced by greasy hair or an oily scalp.
• A scalp that’s overly dry. “Dandruff can also be the result of a too-dry scalp,” says Dr. Gohara. “Also, flaking can be caused by using too many products in the hair, or not washing products out properly — but this isn’t the same thing as dandruff.”
What is scalp psoriasis? The causes and symptoms
“Scalp psoriasis is a completely different animal from dandruff,” says Dr. Gohara. Psoriasis can appear anywhere on the body, she points out, and according to the National Psoriasis Foundation (NPF), 45 to 56% of people who have psoriasis have it on their scalp. It can feel very itchy, and at times burning or painful. Here, more information on the cause of scalp psoriasis:
• “Psoriasis is the result of an over-proliferation of epidermis, the top layer of our skin, resulting in thick, scaly plaques,” says Dr. Gohara.
• The cause of that over-proliferation is an immune dysregulation around skin cells, Dr. Gohara explains. According to the Journal of Psoriasis and Psoriatic Arthritis, psoriasis is what is called an “immune-mediated” disease — meaning that an unknown cause brings about a dysregulation of the immune system that causes inflammation. The overactive immune system revs up the growth of skin cells, which pile up rather than shedding, creating the plaques.
• “Generally, in scalp psoriasis, the plaques are usually very dry, not oily or greasy. And there’s redness or pinkness — or with dark skin, a dark red or purplish color," says Dr. Gohara.
• “Scalp psoriasis can be very disruptive to one’s lifestyle,” says Dr. Gohara. “It’s very obvious — everyone knows if you have it. If you have, say, a heart issue, people don’t see it, but they see the flaking from scalp psoriasis.”
How can you tell if you have scalp psoriasis vs. dandruff?
“The color — that red, pink or purple color — is very distinguishing of scalp psoriasis,” says Dr. Gohara. So are the dry, thick plaques, which can be silvery in color. Scalp psoriasis can also spread beyond the hairline and behind the ears. A dermatologist can help you determine what condition you have.
What are other differences between scalp psoriasis and dandruff?
Dandruff is not associated with systemic problems in the body, Dr. Gohara points out. Psoriasis is associated with an increased risk of arthritis of the small joints or lower back, called psoriatic arthritis, as well as cardiovascular issues related to inflammation.
What are treatments for dandruff?
There are specific over-the-counter shampoos that are designed to treat dandruff, according to the AAD. They contain different ingredients, including salicylic acid (found in Neutrogena’s T/Sal), zinc pyrithione (Head & Shoulders), coal tar (also contained in Neutrogena’s T/Gel), and selenium sulfide (Selsun Blue). And there’s also an OTC anti-yeast shampoo (Nizoral) that’s used to treat dandruff, says Dr. Gohara. Prescription options are also available through your dermatologist.
Dr. Gohara adds that anti-yeast medications are sometimes used to treat dandruff, as well as anti-inflammatory topical steroids (if the dandruff is associated with inflammation or greasy scalp).
What are treatments for scalp psoriasis?
According to the NPF, scalp psoriasis can be difficult to treat because of the hair covering the plaques. Doctors usually start with basics in treating it, says Dr. Gohara, often with prescription topical inflammatory medications, a form of steroid.
If a person has a mild case of scalp psoriasis, there are OTC psoriasis products that can be tried first, says the NPF; look for products that contain salicylic acid or coal tar. Shampoos targeted to help psoriasis can help: “Salicylic acid shampoos cut thru the over-proliferation of the skin’s top layer on the scalp,” says Dr. Gohara. There are other shampoos containing coal tar that can be tried as well.
Phototherapy, which uses UV light to slow cell growth, is also used to treat psoriasis. “As dermatologists, we’re always telling people to avoid UV light, but it’s a very effective anti-inflammatory,” says Dr. Gohara. For scalp psoriasis, a doctor can use a hand-held phototherapy device with a comb to specifically target that area, according to the NPF.
If a person’s psoriasis is moderate to severe and isn’t limited to the scalp — or if their scalp psoriasis hasn’t responded to other treatments — there are oral systemic medications available that target molecules within immune cells, says the NPF. “There are also biologics available to treat psoriasis,” says Dr. Gohara. “These have been a game-changer — they specifically target the problem in the immune system.” These medications and biologics have side effects, which your dermatologist can explain and help you consider if they're a good option for you.
If it's scalp psoriasis, are there lifestyle factors to consider?
“One thing people should be aware of is that stress can worsen psoriasis, because stress increases the hormone cortisol, which in turn increases inflammation,” says Dr. Gohara. So it makes sense to focus on whatever you can do to lower your tension level, whether that means taking yoga classes, practicing mindfulness, carving out time to relax and read or reaping the benefits of daily reflective walks.
Another concern among those with scalp psoriasis is whether it’s safe to dye one’s hair. “I would never tell someone to avoid coloring their hair, but it’s true that psoriasis tends to emerge in areas of the body that are under pressure or trauma,” says Dr. Gohara. “Hair dye, styling products and chemicals can cause trauma to one's skin. So yes, people with scalp psoriasis can get a flare up from coloring their hair. It’s a good idea to have a conversation with your stylist about using gentle formulas.”