How do psoriasis and seborrheic dermatitis differ?
One significant difference between seborrheic dermatitis and scalp psoriasis is their appearance.
Psoriasis that affects the scalp appears powdery and has a silver surface. Seborrheic dermatitis is more likely to appear yellow and greasy.
In this article, we look at other differences in each condition, as well as their possible causes and treatments.
Understanding the differences between seborrheic dermatitis and psoriasis can help people get early treatment from a doctor. A quick diagnosis supports more effective treatment for either condition.
Seborrheic dermatitis symptoms
Seborrheic dermatitis causes greasy, yellow patches on the scalp and skin.
The symptoms of seborrheic dermatitis usually develop on the scalp, although they can sometimes develop on the face, upper chest, and back.
- crusty, white flakes
- greasy, yellow scales
- red and swollen skin
- an itching or burning sensation in the affected area
While psoriasis can affect the scalp, it is more likely to develop in other areas of the body, such as the elbows or knees.
Psoriasis causes raised, scaly patches to appear on the skin. When it develops on the scalp, it can lead to cracking, bleeding skin, and silver-white scales. The skin may feel sore or have a burning sensation.
However, as with seborrheic dermatitis, it can also cause flaking that resembles dandruff. Despite this similarity, the skin around psoriasis lesions is much drier than the skin around sites that seborrheic dermatitis affects.
Types of psoriasis
There are five main types of psoriasis, each of which has different skin involvement.
The most common type of psoriasis is plaque psoriasis.
The condition presents as raised, red patches with a silvery-white buildup of dead skin cells. These lesions can be itchy and painful.
This type of psoriasis takes the form of small, dotted lesions. About 10 percent of people with psoriasis have this version of the condition.
Inverse psoriasis appears as red, smooth, shiny lesions that develop in skin folds, such as the groin, armpits, and backs of the knees.
As inverse psoriasis affects the folds of the skin, these areas can become more prone to yeast or fungal infections.
Pustular psoriasis usually affects the hands and feet. White blisters of pus with a surrounding of red skin are characteristic of the condition.
The rarest and most severe form of psoriasis is erythrodermic psoriasis. This appears as a "fiery" redness that spreads over most of the body and is extremely painful.
People with erythrodermic psoriasis may experience severe itching, and their skin may peel off in sheets. Only about 3 percent of people with psoriasis have erythrodermic psoriasis.
Scientists do not know the exact cause of psoriasis or seborrheic dermatitis. However, researchers believe that genetics play a critical role in both.
Triggers in the environment cause the specific genes that lead to dermatitis and psoriasis to send incorrect instructions to the immune system.
Thinking about any recent exposure to these triggers can help a person identify which condition might be behind a symptom flare.
Triggers for seborrheic dermatitis
Illness may trigger seborrheic dermatitis.
- hormone changes
- harsh detergents
- dry weather
- microorganisms on the skin
Diseases that impact the immune system, such as HIV, can make the symptoms of seborrheic dermatitis worse. Those that affect the nervous system, such as Parkinson's, might also aggravate symptoms.
Triggers for psoriasis
When people have psoriasis, skin cells grow more quickly than they do in others. This causes lesions to build up.
The following can trigger a flare of psoriasis symptoms:
- skin injury
- medications, such as lithium and quinidine
- infection, such as strep throat, bronchitis, and tonsillitis
People who regularly encounter the triggers of psoriasis and seborrheic dermatitis and have a genetic tendency toward psoriasis are at risk of a flare.
Seborrheic dermatitis might develop at any age, and it is a little more common in males than in females.
Males and females are equally as likely to get psoriasis, and it is slightly more common in white people than African Americans.
People can develop psoriasis at any age, although it often occurs between 15 and 35 years of age. In very rare cases, infants may develop psoriasis.
There are several treatments available for both seborrheic dermatitis and psoriasis. Treatments are different for each condition, and the effectiveness of the different approaches can vary from person to person.
Seborrheic dermatitis treatment
A person can treat mild cases of seborrheic dermatitis by applying a topical antifungal cream. Medicated shampoo can also help.
Examples of these include:
- selenium sulfide
- coal tar
- zinc pyrithione
People with more severe seborrheic dermatitis may need treatment with corticosteroids to reduce inflammation.
Corticosteroids may not be appropriate if someone has had previous, long-term exposure to them. If this is the case, a doctor might prescribe a medication they call topical calcineurin inhibitors.
These treatments might also help some people with scalp psoriasis. However, doctors consider them to be off-label medications for psoriasis.
Examples of topical calcineurin inhibitors that a doctor may prescribe off-label include:
- tacrolimus (Protopic)
- pimecrolimus (Elidel)
People with severe seborrheic dermatitis might also use antifungal medication.
Scalp psoriasis treatments
Medicinal shampoos are available to treat scalp psoriasis.
Different types of psoriasis require different interventions. As seborrheic dermatitis most closely resembles scalp psoriasis, this article focuses on treatments for this type.
Treating scalp psoriasis is often complicated and takes time and patience.
Coal-tar products and salicylic acid are useful for treating mild scalp psoriasis. There are also many medicated shampoos available over the counter (OTC) to treat scalp lesions and help reduce itching if the lesions are very mild and only affect a few areas.
Bathing the scalp in warm water or making the scalp damp before applying lotions, creams, and ointments can help make plaques softer. Gently combing the scalp in circular motions can then remove softened plaques from the scalp.
More severe cases of scalp psoriasis may require more intensive topical treatments, such as:
- anthralin (Dritho-Scalp)
- calcipotriene (Dovonex)
- calcipotriene and betamethasone dipropionate (Taclonex)
- tazarotene (Tazorac)
Doctors do not often consider systemic medications as treatments for scalp psoriasis.
They may consider biologics, such as etanercept (Enbrel), that originate from living cells, but these are not the first-line treatment for scalp psoriasis and would be off-label.
People with more severe scalp psoriasis may need to try and combine several treatments before they find the one that works for them.
After repeated use, a person's psoriasis may become less responsive to the medication. If this happens, they may need a combination of treatments, which they can use in rotation.
When to see a doctor
A person should talk to a doctor if they are experiencing the physical effects of seborrheic dermatitis or psoriasis. If a rash, lesion, or pustule does not respond to OTC remedies, it may be one of these chronic disorders.
No test is available to identify either condition. A doctor will ask people questions about their medical history and look at the lesions to decide the cause.
The doctor may also remove a small sample of skin to help confirm their diagnosis.
Seborrheic dermatitis and psoriasis can appear similar but present on the scalp in different ways.
Psoriasis is more likely to appear in other areas of the body alongside the scalp, and several different types may develop. Seborrheic dermatitis, however, tends to develop mainly on the scalp.
The appearance of psoriasis tends to change depending on the type. Seborrheic dermatitis, on the other hand, appears as yellow, greasy scales with red, swollen skin and white flakes.
Most commonly, psoriatic plaques have a silvery surface that may cause itching and pain.
Different treatments are available, and a person should seek a medical opinion if they suspect the presence of either condition.
Can seborrheic dermatitis become psoriasis?
Seborrheic dermatitis cannot become psoriasis. Neither seborrheic dermatitis nor psoriasis change into a different condition.
Psoriasis is a lifelong condition that cannot be contracted and can only flare up once something triggers it.
An independent case of seborrheic dermatitis could lead to a psoriasis flare in someone who already has psoriasis, causing additional stress to manage it, but it will never become psoriasis.Debra Sullivan, PhD, MSN, RN, CNE, COI Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.