Seborrheic dermatitis can sometimes look like other skin conditions or other types of eczema. This can make it difficult to diagnose. Seborrheic dermatitis is a type of eczema that causes a scaly rash on the skin and scalp. It’s a chronic (long-term) skin condition, and symptoms come and go over time, with periods of flare-ups and times when your skin looks clear.

Your healthcare provider may use different tests to rule out other possible causes before confirming that you have seborrheic dermatitis. Once you have a diagnosis, you can begin treatments that help improve your symptoms and clear your skin.

Challenges of Diagnosing Seborrheic Dermatitis

Healthcare providers and dermatologists (skin specialists) mainly diagnose seborrheic dermatitis by examining your skin and reviewing your skin symptoms. Symptoms most often appear on parts of the body that have more sebaceous glands, like the scalp, face, and chest.

An overgrowth of Malassezia yeast, which naturally occurs on the skin, may play a role in causing inflammation and making seborrheic dermatitis symptoms worse.

Common symptoms include:

• White, itchy flakes (dandruff) on the scalp and under facial hair
• Scaly, red, or discolored patches around the eyes or eyebrows
• Itchy skin
• Red or discolored rashes in skin folds and creases
• Pink or discolored plaques, or areas of thickened skin, on the face
• Small, raised bumps
• Inflamed hair follicles on the chest and cheeks

Because these symptoms can also appear in other inflammatory skin conditions, your healthcare provider may do a differential diagnosis. For a differential diagnosis, your doctor will look at your symptoms, run some tests, and rule out other causes before confirming seborrheic dermatitis.

To help your healthcare provider make the right diagnosis, it can be helpful to track your symptoms over time. Note when your skin is clear and when you have flares. Write down where symptoms appear, how long they last, what they feel like, and whether any home treatments made them better or worse. Taking pictures of your symptoms can also help you and your doctor see how your skin changes over time.

How Do Doctors Diagnose Seborrheic Dermatitis?

Healthcare providers usually diagnose seborrheic dermatitis by doing a physical exam and looking at your skin. If the diagnosis is unclear, your dermatologist may do a simple test called a skin biopsy.

Blood tests aren’t usually needed unless your healthcare provider thinks another medical condition could be causing your seborrheic dermatitis symptoms.

Physical Exam

Your healthcare provider will likely start by examining your skin for common signs of seborrheic dermatitis, such as:

• Dandruff or scales on your scalp or in facial hair (like a mustache or beard)
• Greasy scales on your scalp
• Patches or plaques on your face, especially if they appear on both sides
• Rashes on other parts of your body, such as under your breasts, armpits, or in the groin area

They may also ask if your symptoms come and go (flares) or if they stay the same over time.

Skin Biopsy

If you have inflamed areas of skin that aren’t obviously seborrheic dermatitis, your healthcare provider may order a skin biopsy. In this test, a small piece of skin is removed and looked at under a microscope. The skin sample is stained with special chemicals that help healthcare providers see different proteins, immune cells, and other structures in the skin.

There are three types of common skin biopsies: punch biopsy, shave biopsy, and excisional biopsy. For seborrheic dermatitis, dermatologists often use a shave biopsy or a punch biopsy. These methods collect a sample of skin from the top layer of skin (known as the epidermis) and a little bit of the underlying dermis, which is affected in seborrheic dermatitis.

A pathologist (a doctor who specializes in studying tissues and cells) will then look at the skin biopsy. Seborrheic dermatitis under a microscope can look very similar to other skin diseases. The pathologist may see inflammation and immune cells gathered around hair follicles and blood vessels.

The blood vessels may also look wider than normal, which can make the skin appear red or discolored. Crusts on the skin may contain certain immune cells called neutrophils.

What Can Be Mistaken for Seborrheic Dermatitis?

Seborrheic dermatitis has some of the same symptoms as many other skin conditions, which can make diagnosis tricky. Some conditions that may be confused with seborrheic dermatitis include:

• Atopic dermatitis — A type of eczema that causes itchy, inflamed, dry skin
• Contact dermatitis — A rash that appears when your skin touches something you’re allergic to or irritated by
• Psoriasis — Causes thick, dry, scaly patches of skin
• Rosacea — Causes redness or a flushed look on the face, on lighter skin tones, and a dusky or dark look on the face on darker skin tones
• Discoid lupus — A chronic condition that causes disk-shaped rashes on the face and scalp
• Bacterial or fungal skin infections — Such as impetigo, candidiasis, erythrasma, or ringworm (tinea capitis)
• Lichen simplex chronicus — Causes discolored, dry, itchy skin
• Nummular dermatitis — Causes coin-shaped, discolored rashes
• Secondary syphilis — A stage of syphilis that can cause a rash on the palms of the hands and soles of the feet

Healthcare providers will pay close attention to where rashes, lesions, and plaques appear on the body, as this helps them tell skin conditions apart. They also look at the appearance and texture of the skin. For example, psoriasis scales usually have a white-silver coating, while seborrheic dermatitis scales are often yellow.

If your healthcare provider suspects a fungal infection, such as tinea capitis, they may run additional tests. One test is a fungal culture, which checks for fungus growth from a small skin sample, or a PAS stain test, which can be used on a skin biopsy to confirm whether fungus is present.

Other Health Conditions Related to Seborrheic Dermatitis

Some health conditions can make a person more likely to develop seborrheic dermatitis. These include human immunodeficiency virus (HIV), Parkinson’s disease, and other skin conditions, such as acne or psoriasis.

If your healthcare provider thinks another health problem might be linked to your symptoms, they may order additional tests or refer you to a specialist. Treating any underlying condition can help improve your seborrheic dermatitis symptoms.

Read more about conditions related to seborrheic dermatitis.

Final Diagnosis and Treatment

Once your dermatology provider rules out other conditions and makes a diagnosis of seborrheic dermatitis, they can prescribe appropriate treatments to improve your symptoms and help clear your skin. These may include one or more therapies, such as:

• Dandruff shampoos that contain zinc pyrithione, tar, salicylic acid, or selenium sulfide
• Shampoos medicated with antifungal ingredients (ketoconazole)
• Topical corticosteroid creams or lotions
• Topical calcineurin inhibitors
• Other topical creams, shampoos, foams, or more

Read more about treatments for seborrheic dermatitis.

Let your healthcare provider know if your skin doesn’t clear after using these treatments. Your symptoms may be caused by another skin condition, which will require a new diagnosis and treatment plan, or adjustments to your current treatment plan.

Join the Conversation

On MySebDermTeam, people share their experiences with seborrheic dermatitis, get advice, and find support from others who understand.

What treatments have you tried for seborrheic dermatitis? What advice do you have for people living with the condition? Let others know in the comments below.