Seborrheic dermatitis is a common chronic, inflammatory skin disorder.
Seborrheic dermatitis symptoms appear slowly and mostly the first symptom is flaky skin and scalp. Symptoms develop anyplace on the skin of the face, back of the ears and in places where the skin folds are seen. Flakes may be yellow, white or grayish. The skin near the eyelashes, forehead, nose, chest and upper back can have redness and flaking.
In serious conditions, yellowish to reddish scaly pimples are seen behind both pinnae, inside the ear canal, topping the eyebrows, on the nasal bridge, along the hairline, around the nose, chest, and upper back.
Generally, patients experience little redness, scaly skin lesions and in few cases hair loss. Various other symptoms are patchy scaling or hard coating on the scalp, red, greasy skin enclosed with flaky white or yellow scales, intense itching, pain and yellow or white scales that can be attached to the shaft of hair.
Seborrheic dermatitis in infants younger than three months can present as thick, oily, yellowish crust surrounding the hairline and on the scalp. This condition is also known as cradle cap. Itching is not common in infants. Commonly, a persistent diaper rash develops along with the scalp rash. Generally, when the rash develops in infants it resolves on its own in a few days, without any treatment, whereas in adults the symptoms can last from couple of weeks to years.
Doctors can generally determine seborrheic dermatitis by a simple physical examination or they might scrape off skin cells for examination (biopsy) to rule out conditions with some symptoms similar to seborrheic dermatitis like psoriasis, atopic dermatitis and rosacea.
Creams, shampoos or ointments that control inflammation like hydrocortisone, fluocinolone or desonide which are corticosteroids are applied to the scalp or other troubled area. They are efficient and simple to use. In case they are used for a long period of time continuously, than they can lead to side effects like thinning skin or striae on skin and must be stopped soon.
Antifungal shampoos when used along with a stronger medication are very effective. Ketoconazole shampoo can be effective when used with clobetasol scalp product in turns twice weekly.
The antifungal medication terbinafine may be a treatment option.
Medications that affect your immune system are also beneficial in the treatment. Therefore creams or lotions having calcineurin inhibitors tacrolimus and pimecrolimus may be adequate and have lesser side effects as compared to corticosteroids.
Light therapy along with medicines is a method of treatment that combines psoralen with light therapy (photochemotherapy). Once psoralen is taken by mouth or is applied on affected skin, the person is exposed to ultraviolet light. People with thick hair may not be benefited much with this therapy.
Antihistamines are used primarily to reduce itching. The research studies propose that some antihistamines have anti-inflammatory properties .
Cradle cap typically disappears on its own as a child develops. Other types of seborrheic dermatitis generally respond to treatment with shampoos and medication.
The exact cause is yet unknown, but the disease is thought to be the result of a combination of factors like microbes, sebum, and some trigger factors. At present various studies suggest, that a weakened immune system, the inadequacy of particular nutrients, or problems with the nervous system are causes of this condition.
Seborrheic dermatitis has a prevalence of about 1 to 5%. The incidence among patients with human immunodeficiency disease (HIV)/acquired immunodeficiency syndrome (AIDS) is about 34 to 83%.
In infants, seborrheic dermatitis is also known as cradle cap. It is due to the maternal androgens and affects up to 70% infants in the first three months of infancy. Recurrence is common around puberty and post 50 years age. Males are affected more than females by a narrow margin.
Seborrheic dermatitis can be due to an inflammatory reaction to multiplication of Malassezia, a type of yeast  . Malassezia globosa is the form of yeast found on the scalp, whereas Malassezia furfur (called previously as Pityrosporum ovale) and Malassezia restricta are the other two types that are seen. The yeast yields poisonous substances that irritate and burn the skin. Individuals suffering from seborrheic dermatitis seem to have low resistance to the yeast. Anyhow, the degree of colonization might be lesser in affected skin as compared to the unaffected skin.
Malassezia dissolves human sebum, dispensing a blend of saturated and unsaturated fatty acids. It picks up the needed saturated fatty acids, leaving behind unsaturated fatty acids. The unsaturated fatty acids penetrate the stratum corneum. Due to their non-consistent structure, they break the skin's barrier function which results in irritation, causing dandruff and seborrheic dermatitis.
Factors like genetic, hormonal, environmental and immune-system are seen to be responsible in causing seborrheic dermatitis  .
In children, increased intake of vitamin A can lead to seborrheic dermatitis. Deficiency of vitamins pyridoxine (vitamin B6) , biotin, and riboflavin (vitamin B2) can also cause it.
Good personal hygiene is extremely essential for patients at a higher risk of developing the condition. Daily bathing and hair washes are recommended, especially for those having an oily skin. A clean scalp is a must to avoid outburst of seborrheic dermatitis. Natural and artificial UV radiations help in restricting the production of Malassezia yeast .
Pre-existing medical conditions that might predispose to seborrheic dermatitis should be attended to on a priority basis. As doctors do not know what causes seborrheic dermatitis, it cannot be prevented with precision, but the symptoms can be controlled with effective treatment.
Seborrheic dermatitis does not have any harmful effect on your general health, but it can be distressing. It can cause embarrassment as it presents in the form of scaling on the exposed areas of the body like face, scalp, folds around the nose etc along with severe itching many a times. Neither is it a communicable condition, nor an evidence of low personal hygiene.
The true cause of the disease is not known but many theories have been put forth and hence it’s advisable to maintain personal hygiene to keep it at bay or under control like washing your skin regularly and rinsing off the soap completely from the body. Avoid using harsh soaps and use a moisturizer regularly. Avoid products that contain alcohol as they can cause a flare up. Wear pure cotton clothing as it reduces irritation. Avoid scratching as it tends to increase skin irritation and the chances of infection. Along with these measures, you can always seek medical help from a professional who can prescribe medicated creams, lotions, shampoos etc. to treat this condition. Sometimes even meditation, yoga and other stress relieving techniques can help in easing this skin condition.