Seborrhoeic dermatitis, also known as seborrhea, is a long-term skin disorder. Symptoms include red, scaly, greasy, itchy, and inflamed skin. Areas of the skin rich in oil-producing glands are often affected including the scalp, face, and chest. It can result in social or self-esteem problems. In babies, when the scalp is primarily involved, it is called cradle cap. Dandruff is a milder form of the condition, without associated inflammation.
The cause is unclear but believed to involve a number of genetic and environmental factors. Risk factors include poor immune function, Parkinson disease, epilepsy, and Down syndrome. The condition may worsen with stress or during the winter. It is not a result of poor hygiene. Diagnosis is typically based on the symptoms.
The typical treatment is antifungal cream and anti-inflammatory agents. Specifically ketoconazole or ciclopirox are effective. It is unclear if other antifungals, such as miconazole, are equally effective as they have been poorly studied. Other options may include coal tar and phototherapy.
The condition is most common in those around the age of 50, during puberty, and among those less than three months old. In adults about 2% of people are affected. Males are more often affected than females. Up to 40% of babies may be affected to some degree.
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Signs and symptoms
Seborrhoeic dermatitis' symptoms appear gradually, and usually the first signs are flaky skin and scalp. Symptoms occur most commonly anywhere on the skin of the scalp, behind the ears, on the face, and in areas where the skin folds. Flakes may be yellow, white or grayish. Redness and flaking may also occur on the skin near the eyelashes, on the forehead, around the sides of the nose, on the chest, and on the upper back.
In more severe cases, yellowish to reddish scaly pimples appear along the hairline, behind the ears, in the ear canal, on the eyebrows, on the bridge of the nose, around the nose, on the chest, and on the upper back.
Commonly, patients experience mild redness, scaly skin lesions and in some cases hair loss. Other symptoms include patchy scaling or thick crusts on the scalp, red, greasy skin covered with flaky white or yellow scales, itching, soreness and yellow or white scales that may attach to the hair shaft.
Seborrhoeic dermatitis can occur in infants younger than three months and it causes a thick, oily, yellowish crust around the hairline and on the scalp. Itching is not common among infants. Frequently, a stubborn diaper rash accompanies the scalp rash. Usually, when it occurs in infants the condition resolves itself within days and with no treatment.
In adults, symptoms of seborrhoeic dermatitis may last from a few weeks, to years. Many patients experience alternating periods of inflammation. The condition is referred to a specialist when self-care has proven unsuccessful.
Causes
The specific causes are not known. Current theories for the cause of the disease include a weakened immune system, the lack of specific nutrients (for example zinc), or issues with the nervous system.
Fungal
Seborrhoeic dermatitis may involve an inflammatory reaction to a proliferation of a form of the yeast Malassezia, though this has not been proven.
The main species of yeast found on the scalp of those with the condition is Malassezia globosa, others being Malassezia furfur (formerly known as Pityrosporum ovale) and Malassezia restricta. It has been suggested that the yeast produces toxic substances that irritate and inflame the skin. Patients with seborrhoeic dermatitis appear to have a reduced resistance to the yeast. However, the colonization rate of affected skin may be lower than that of unaffected skin.
Only saturated fatty acids (FAs) have been shown to support Malassezia growth. It has also been shown that while number density of M. globosa and M. restricta do not directly correlate to dandruff presence or severity, removal correlates directly with amelioration of flaking. Furthermore, in dandruff-susceptible individuals pure oleic acid, an unsaturated FA and Malassezia metabolite, induces flaking in the absence of Malassezia by direct effects on the host skin barrier. These findings support the following hypothesis:
Malassezia hydrolyze human sebum, releasing a mixture of saturated and unsaturated fatty acids. They take up the required saturated FAs, leaving behind unsaturated FAs. The unsaturated FAs penetrate the stratum corneum. Because of their non-uniform structure, they breach the skin's barrier function. This barrier breach induces an irritation response, leading to dandruff and seborrhoeic dermatitis.
Other
Genetic, environmental, hormonal, and immune-system factors have been shown to be involved in the manifestation of seborrhoeic dermatitis.
Seborrhoeic dermatitis may be aggravated by illness, psychological stress, fatigue, sleep deprivation, change of season and reduced general health.
In children, excessive vitamin A intake can cause seborrhoeic dermatitis. Lack of biotin, pyridoxine (vitamin B6), or riboflavin (vitamin B2) may be a cause in babies.
Those with immunodeficiency (especially infection with HIV) and with neurological disorders such as Parkinson's disease (for which the condition is an autonomic sign) and stroke are particularly prone to it.
Prevention
Daily use of an over-the-counter or prescription anti-fungal shampoo may help in those with recurrent episodes of the disease.
Both natural and artificial UV radiation curbs the growth of Malassezia yeast.
Management
Medications
A number of medications are able to control seborrheic dermatitis including: certain antifungals, topical corticosteroids, and keratolytics such as topical urea, as well as antiandrogens and antihistamines.
Antifungals
The topical antifungal medications ketoconazole and ciclopirox have the best evidence. It is unclear if other antifungals are equally effective as this has not been studied.
Antiandrogens
Seborrhea is recognized as an androgen-sensitive condition - that is, it is caused or aggravated by androgen sex hormones such as testosterone and dihydrotestosterone - and is a common symptom of hyperandrogenism (e.g., that seen in polycystic ovary syndrome). In addition, seborrhea, as well as acne, are commonly associated with puberty due to the steep increase of androgen levels at that time.
In accordance with the involvement of androgens in seborrhea, antiandrogens, such as cyproterone acetate, spironolactone, and flutamide, are highly effective in alleviating the condition. As such, they are used in the treatment of seborrhea, particularly severe cases. While beneficial in seborrhea, effectiveness may vary with different antiandrogens; for instance, spironolactone (which is regarded as a relatively weak antiandrogen) has been found to produce a 50% improvement after three months of treatment, whereas flutamide has been found to result in an 80% improvement within three months. Cyproterone acetate is similarly more potent and effective than spironolactone, and results in considerable improvement or disappearance of acne and seborrhea in 90% of patients within three months.
Systemic antiandrogen therapy should only be used to treat seborrhea in women, as these drugs can result in feminization (e.g., gynecomastia), sexual dysfunction, and infertility in males. In addition, antiandrogens theoretically have the potential to feminize male fetuses in pregnant women, and for this reason, should always be combined with effective contraception in sexually active women who can or may become pregnant.
Antihistamines
Antihistamines are used primarily to reduce itching, if present. However, research studies suggest that some antihistamines have anti-inflammatory properties.
Others
- Coal tar can be effective, but, although no significant increased risk of cancer in human treatment with coal tar shampoos has been found, caution is advised since coal tar is carcinogenic in animals, and heavy human occupational exposures do increase cancer risks.
- Pimecrolimus topical cream immunosuppressant
- Isotretinoin -- As a last resort in refractory disease, sebosuppressive agent isotretinoin may be used to reduce sebaceous gland activity. However, isotretinoin has potentially serious side effects and few patients with seborrhea are appropriate candidates for therapy.
Phototherapy
Some recommend photodynamic therapy using UV-A and UV-B laser or red and blue LED light to inhibit the growth of Malassezia fungus and reduce seborrhoeic inflammation.
Epidemiology
Seborrhea affects 1 to 5% of the general population. It is slightly more common in men, but affected women tend to have more severe symptoms. The condition usually recurs throughout a person's lifetime. Seborrhea can occur in any age group but usually starts at puberty and peaks in incidence at around 40 years of age. It can reportedly affect as many as 31% of older people. Severity is worse in dry climates.
Source of the article : Wikipedia
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