Seborrheic dermatitis can often look like other skin conditions, making 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 (ongoing) skin condition, and symptoms come and go over time with periods of clear skin and flare-ups.

Your doctor or dermatologist will use a few different tests to rule out other conditions and make a seborrheic dermatitis diagnosis. After you receive a diagnosis, you’ll be able to get the treatments you need to improve your symptoms and help clear your skin.

Challenges of Diagnosing Seborrheic Dermatitis

Doctors and dermatologists mainly diagnose seborrheic dermatitis by taking an account of all of your skin symptoms. Symptoms usually appear in areas of the skin with more sebaceous glands, like the scalp, face, and chest. Overgrowth of Malassezia yeast, which naturally occurs on the skin, may also contribute to inflammation and worsening of seborrheic dermatitis symptoms. Common symptoms include:

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

Many of these symptoms are also seen in other inflammatory skin conditions, which makes it difficult for your doctor or dermatologist to tell them apart. To avoid misdiagnosing you with another condition, your health care provider will make a differential diagnosis. For a differential diagnosis, a doctor will look at your symptoms, conduct some tests, and try to rule out any other conditions that may be causing your skin symptoms.

To help your doctor or dermatologist make the correct diagnosis, you could track your symptoms over time, to see when your skin is clear and when you have flares. Be sure to write down where symptoms occur, how long they last, what they feel like, and any treatments you tried at home that helped or made them worse. Pictures of your symptoms are helpful to track how their appearance changes over time.

Tests for Diagnosing Seborrheic Dermatitis

To diagnose seborrheic dermatitis, your doctor or dermatologist will perform a physical exam, which usually leads to a diagnosis. If the diagnosis is unclear, your dermatologist may perform a biopsy to examine your skin under a microscope. Typically, they don’t need to run any blood tests, unless they think you have an underlying condition that may be causing seborrheic dermatitis. Depending on your symptoms, they’ll order more tests to get to the correct diagnosis.

Physical Exam

Your doctor or dermatologist will likely start with a physical examination of your skin to look for symptoms of seborrheic dermatitis. These include:

• The presence of dandruff or scales on your scalp or in facial hair, such as a mustache or beard
• The formation of greasy scales on your scalp
• The presence of plaques on your face and whether they’re symmetrical (the same on both sides)
• The location of rashes on your body, such as under your breasts, armpits, or groin

They may also ask if you have symptom flares or if they’re persistent (they don’t go away after some time).

Skin Biopsy

If you have inflamed areas of skin, your doctor or dermatologist may order a skin biopsy. This test involves removing a small piece of skin to examine it under a microscope. Sometimes, the skin sample is stained with chemicals to help doctors look at different proteins, immune cells, or structures in the skin.

There are three types of skin biopsies: punch biopsy, shave biopsy, and excisional biopsy. To test for seborrheic dermatitis, your dermatologist may use a shave biopsy or punch biopsy. These methods take a piece of skin from the outermost layer (known as the epidermis) and a little bit of the underlying dermis, which is affected in seborrheic dermatitis.

Pathologists, doctors who specialize in studying tissues and cells, look at skin biopsies. Under a microscope, seborrheic dermatitis looks much different than other skin diseases. The pathologist may see inflammation and immune cells clustered around the hair follicles and blood vessels.

There may also be extra fluid in between the cells in the epidermis, which looks like empty space under a microscope. The blood vessels in the skin may also be smaller and wider than normal, which causes reddening or discoloration. Crusts from the skin may also have specific types of immune cells in them, such as neutrophils.

Differential Diagnosis and Other Skin Conditions

Seborrheic dermatitis has overlapping symptoms with many other skin conditions, including:

• Atopic dermatitis — A type of eczema that causes itchy, inflamed, dry skin
• Contact dermatitis — Itchy skin and rashes from coming into contact with a substance you’re allergic to
• Psoriasis — Rash with dry, scaly patches
• Rosacea — Blushing or discolored appearance of the face
• Discoid lupus — A chronic condition that causes disk-like rashes on the scalp and face
• Bacterial or fungal skin infections — Impetigo, candidiasis, erythrasma, and tinea capitis
• Lichen simplex chronicus — Discolored, dry, itchy skin
• Nummular dermatitis — Coin-shaped, discolored rashes
• Secondary syphilis — A condition that causes a rash on the palms of the hands and soles of the feet

Because there are so many similar conditions, doctors and dermatologists may have a hard time diagnosing seborrheic dermatitis. Often, they look at where rashes, lesions, and plaques are found, which can point to a certain diagnosis. These skin changes can also look different compared to one another. For example, psoriasis skin scales typically have a white-silver coating, while seborrheic dermatitis scales are often pink, red, or a shade darker or lighter than your natural skin tone. Seborrheic dermatitis is also a chronic condition that has periods of flares and clear skin, while some other skin conditions do not.

Your doctor or dermatologist may also use a skin biopsy to tell the difference between seborrheic dermatitis and other skin conditions. Skin biopsies from people with seborrheic dermatitis look different under a microscope compared to other conditions. For example, one study found many differences between skin samples in people with seborrheic dermatitis and psoriasis.

If your doctor or dermatologist thinks you may have a fungal infection, such as tinea capitis, they may run additional tests. One test is a fungal culture, where a sample is taken from your skin to see if any fungus grows from it, or a PAS staining test can be done on the skin biopsy to detect fungus.

Other Health Conditions Related to Seborrheic Dermatitis

People with certain health conditions, like human immunodeficiency virus (HIV) or Parkinson’s disease, have an increased risk of seborrheic dermatitis. Having other skin conditions, such as acne or psoriasis, can also increase your risk of developing seborrheic dermatitis. Your doctor or dermatologist may choose to run additional tests to diagnose and treat these conditions, which 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 final diagnosis of seborrheic dermatitis, you can receive appropriate treatments to improve your symptoms and help clear your skin. These can include one or more therapies, including:

• Dandruff shampoos that contain zinc pyrithione, coal tar, salicylic acid, or selenium sulfide
• Medicated shampoos with antifungals such as ketoconazole or cicloprox
• Topical corticosteroid creams or lotions
• Calcineurin inhibitors, including tacrolimus or pimecrolimus

Read more about treatments for seborrheic dermatitis.

Let your doctor or dermatologist know if your skin doesn’t clear after using these treatments. You may have another skin condition causing your symptoms, which will require a new diagnosis and treatment plan.

Talk With Others Who Understand

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

What treatments have you tried for seborrheic dermatitis? What advice do you have for others living with the condition? Share your tips and experiences in a comment below or in your Activity feed.