Though seborrheic dermatitis and psoriasis have notable differences, their commonalities can make it difficult to tell the conditions apart. Both cause itchy and flaky skin, for example, and both often affect the scalp. It’s also possible to have both conditions at the same time, which is referred to as sebopsoriasis.

One member of MyPsoriasisTeam — the online network and support group for people with psoriasis — described the confusion they’ve experienced trying to get an accurate diagnosis: “I have been told by my dermatologist I have seborrheic dermatitis. My primary care provider said it’s psoriasis.”

Understanding the differences between seborrheic dermatitis and psoriasis is essential in getting an accurate diagnosis and appropriate treatment. Here are some key differences that can help you better understand these two skin diseases and ensure you get the care you need.

1. Seborrheic Dermatitis Patches Look Different From Psoriasis Plaques

While the two conditions have similarities, there are some distinctive differences between seborrheic dermatitis symptoms and psoriasis symptoms.

Seborrheic Dermatitis Symptoms

Seborrheic dermatitis — a common type of eczema — causes patches of skin to become itchy, scaly, flaky, and discolored. It commonly affects the scalp and causes dandruff, but it can affect other areas of the body, including the:

• Hairline
• Face
• Chest
• Upper back
• Skin folds, such as the navel, groin, and under the breasts

Psoriasis Symptoms

On the other hand, plaque psoriasis — the most common type of psoriasis — causes thick, raised lesions (plaques) that are larger than seborrheic dermatitis flares. They often have gray or silvery flakes and bleed easily if scratched. Psoriasis lesions can be red, brown, or purple. They can also be itchy, painful, and susceptible to infection. Psoriasis lesions have clearly defined edges. In contrast, in seborrheic dermatitis, scaly skin has less clear boundaries.

Psoriasis can occur anywhere on the body. It’s commonly found on the elbows, knees, and lower back, where plaques tend to be dry. Psoriasis plaques on the scalp, however, may be greasy. In severe cases, psoriasis on the scalp can cause hair loss.

In approximately one-third of psoriasis cases, people develop psoriatic arthritis and experience symptoms such as joint pain, heel pain, and morning stiffness.

2. Seborrheic Dermatitis May Be Triggered by Malassezia Yeast

Both seborrheic dermatitis and psoriasis are immune-mediated diseases, which means they’re caused by immune system dysfunction. Both diseases have genetic and environmental risk factors. But each condition affects the skin differently.

Causes of Seborrheic Dermatitis

Scientists believe seborrheic dermatitis is triggered by Malassezia yeast, a fungus also known as pityrosporum. Malassezia is a fungal microorganism that’s normally found on skin. But in people with seborrheic dermatitis, Malassezia yeast growth can cause the immune system to overreact, leading to skin inflammation and an itchy, flaky rash.

Seborrheic dermatitis occurs in areas of the body with higher concentrations of sebaceous glands, or oil glands. These glands produce sebum, an oily substance that helps protect the skin barrier. Oily sebum is what makes skin affected by seborrheic dermatitis sometimes feel greasy.

Other seborrheic dermatitis triggers include:

• Emotional stress
• Irritating chemicals or soaps
• Reactions to certain medications

Seborrheic dermatitis can occur alongside or as a result of other health conditions, including:

• Parkinson’s disease
• HIV and AIDS
• Metabolic syndrome
• Mental health conditions
• Bacterial and fungal infections
• Other skin diseases, such as atopic dermatitis, rosacea, and psoriasis

Causes of Psoriasis

Psoriasis is also believed to be caused by disorders of the immune system. However, the skin reacts very differently in psoriasis than in seborrheic dermatitis. In psoriasis, an overactivation of the immune system causes skin cells to reproduce several times faster than normal skin cells do. Skin cells naturally flake off as they die, but in people with psoriasis, skin cells rapidly accumulate into thick lesions with excessive flaking.

Psoriasis may be triggered by:

• Skin injury
• Cold or dry weather
• Illness or infection
• Certain medications

Psoriasis is considered a systemic inflammatory condition and is associated with a number of comorbidities, such as:

• Cardiovascular disease
• Inflammatory bowel disease (IBD)
• Psoriatic arthritis
• Depression

3. A Seborrheic Dermatitis Diagnosis Is Less Likely To Require a Skin Biopsy

Doctor’s will usually determine a seborrheic dermatitis diagnosis from a physical skin examination and a review of a person’s symptoms. On rare occasions, a doctor may recommend a biopsy to confirm a seborrheic dermatitis diagnosis. A biopsy entails scraping off a sample of inflamed skin to examine under a microscope. They may recommend the biopsy if you don’t respond to treatment, or if you have signs or symptoms of other skin conditions.

A psoriasis diagnosis is generally handled in a similar way. In some cases, a doctor will be able to determine you have a form of psoriasis based on a physical examination. However, there are many types of psoriasis that can present a variety of symptoms. Moreover, some of these symptoms overlap with those of other skin conditions. As such, it’s more likely your doctor will recommend a biopsy for psoriasis than for seborrheic dermatitis to make a definitive diagnosis.

Biopsies can help determine whether you have psoriasis or seborrheic dermatitis by showing how your cells are being affected. For instance, a seborrheic dermatitis biopsy tends to show blockage in hair follicles, where oily secretions of sebum can build up. Unfortunately, even with a biopsy, making a precise diagnosis can sometimes be difficult.

4. Seborrheic Dermatitis Treatment May Include Topical and Systemic Antifungals

There’s no known cure for either seborrheic dermatitis or psoriasis. Treatment plans are aimed at relieving or eliminating symptoms and improving quality of life. People with either condition (or both) can benefit from careful at-home skin care to help moisturize and relieve dry skin, itchiness, and flaking in affected areas.

Talk to your dermatology care providers about treatment options that may be appropriate for you and how to best manage your home skin care. Always get medical advice before changing a treatment plan or trying a new product.

Treatment Options for Seborrheic Dermatitis

First-line treatment options for seborrheic dermatitis include topical antifungal medications that are available as gels, ointments, lotions, creams, foams, and shampoos. Over-the-counter (OTC) antifungal topicals are available, such as 1 percent ciclopirox (Loprox) and 1 percent ketoconazole. Your doctor may recommend a prescription-strength topical antifungal.

Anti-inflammatory topical treatment options such as prescription corticosteroids or calcineurin inhibitors — pimecrolimus (Elidel) or tacrolimus (Protopic) — are effective for some people with seborrheic dermatitis.

Doctors sometimes recommend oral systemic antifungal medication when topical treatments don’t relieve symptoms.

Treatment Options for Psoriasis

First-line treatment options for psoriasis also include topical therapies. Your doctor may recommend OTC and prescription-strength topical steroids, along with vitamin D analogs. OTC products that contain salicylic acid, coal tar, or anti-itch medications like hydrocortisone or camphor may be effective. Natural remedies such as aloe vera gel or jojoba oil may be effective for some people.

Topicals may be combined with other psoriasis treatments, such as ultraviolet phototherapy (light therapy) or systemic medications, such as methotrexate, cyclosporine, biologic drugs, or oral small-molecule drugs.

5. Seborrheic Dermatitis Is More Common Than Psoriasis

Seborrheic dermatitis is considered a common skin condition, affecting approximately 11 percent of the population. Men have a higher rate of seborrheic dermatitis than women. The condition usually occurs in infants or in people between 30 and 60 years old.

People with oily skin are more likely to develop seborrheic dermatitis. People with coinciding health conditions, such as organ transplants, some types of lymphoma, Parkinson’s disease, and Down syndrome have higher rates of seborrheic dermatitis. A family history of psoriasis also increases the risk of developing seborrheic dermatitis.

Psoriasis is also a common condition, affecting 2 percent to 3 percent of the U.S. population. People of any age can develop psoriasis, but it typically develops between the ages of 20 and 30 or 50 and 60. A family history of psoriasis increases the risk of developing the disease. People with coinciding health conditions linked to psoriasis are also at higher risk.

Although people of all skin types can develop seborrheic dermatitis or psoriasis, both conditions are more prevalent in people with white skin.

Find Your Team

MySebDermTeam is the social network for people with seborrheic dermatitis and their loved ones. On MySebDermTeam, more than 400 members come together to ask questions, give advice, and share their stories with others who understand life with seborrheic dermatitis.

Have you wondered about the difference between seborrheic dermatitis and psoriasis? Which treatments have helped relieve your symptoms? Share your experience in the comments below, or start a conversation by posting on your Activities page.