Seborrheic dermatitis

• Patchy scaling or thick crusts on the scalp
• Yellow or white scales that may attach to the hair shaft
• Red, greasy skin covered with flaky white or yellow scales
• Itching or soreness
• Skin flakes or dandruff

Seborrheic dermatitis predominately affects the scalp, but it can occur between folds of skin and on skin rich in oil glands. It can occur in and between your eyebrows, on the sides of your nose and behind your ears, over your breastbone, in your groin area, and sometimes in your armpits. You may experience periods when your signs and symptoms improve alternating with times when they worsen.

In infants, seborrheic dermatitis of the scalp is known as cradle cap. The patches may be thick, yellow, crusty or greasy. In most cases, the condition isn't itchy for infants like it is for older children or adults.

Causes

Though the exact cause of seborrheic dermatitis isn't known, several contributing factors seem to play a role, including:

• A yeast (fungus) called malassezia that grows in the oily secretion found on the skin (sebum) along with bacteria — antifungal treatments, such as ketoconazole (Nizoral), are often effective, supporting the idea that yeast is a contributing factor
• Stress and fatigue
• Change of season — outbreaks are usually worse in the winter
• Neurological conditions — seborrheic dermatitis may also occur more frequently in people who have certain neurological conditions, such as Parkinson's disease
• HIV/AIDS — people with HIV/AIDS have an increased risk of seborrheic dermatitis

Diagnosis

Your doctor may diagnose seborrheic dermatitis by:

• Physical examination — talking to you about your symptoms and examining your skin and scalp
• Skin biopsy or other tests — which are sometimes necessary to confirm the diagnosis and to rule out other types of dermatitis

Conditions that are similar to seborrheic dermatitis include:

• Atopic dermatitis. This form of dermatitis is a chronic condition that causes itchy, inflamed skin. Most often, it occurs in the folds of the elbows, on the backs of the knees or on the front of the neck. It tends to flare periodically and then subside for a time, even up to several years.
• Psoriasis. A skin disorder characterized by dry, red skin covered with silvery scales. Like seborrheic dermatitis, psoriasis can affect the scalp and cause flaky dandruff. Psoriasis patches can range from a few spots of dandruff-like scaling to major eruptions that cover large areas of the body.
• Ringworm of the scalp (tinea capitis). Ringworm of the scalp is a type of fungal infection that is most common in toddlers and school-age children. It causes red, itchy, bald-looking patches on the scalp.

References

http://www.mayoclinic.org/diseases-conditions/seborrheic-dermatitis/basics/definition/con-20031872

http://emedicine.medscape.com/article/1108312-overview

http://www.medicinenet.com/seborrheic_dermatitis/article.htm

http://www.webmd.com/skin-problems-and-treatments/seborrheic-dermatitis-medref