[2][3] Areas of the skin rich in oil-producing glands are often affected including the scalp, face, and chest.

[2] Mild seborrhoeic dermatitis of the scalp may be described in lay terms as dandruff due to the dry, flaky character of the skin.

[2][4] Risk factors for seborrhoeic dermatitis include poor immune function, Parkinson's disease, and alcoholic pancreatitis.

[11] Seborrhoeic dermatitis' symptoms are typically mild and appear gradually but are often persistent, lasting weeks to years.

[8] Seborrhoeic dermatitis can also occur quickly and severely in patients with Human Immunodeficiency Virus (HIV).

[1][14] In addition to the presence of Malassezia, genetic, environmental, hormonal, and immune-system factors are necessary for and/or modulate the expression of seborrhoeic dermatitis.

[15][16] The condition may be aggravated by illness, psychological stress, fatigue, sleep deprivation, change of season, and reduced general health.

[17] The condition is thought to be due to a local inflammatory response to overgrowth by Malassezia fungi species in sebum-producing skin areas including the scalp, face, chest, back, underarms, and groin.

[3][14] This is based on observations of high counts of Malassezia species in skin affected by seborrhoeic dermatitis and on the effectiveness of antifungals in treating the condition.

[14] Species of Malassezia implicated in Seborrhoeic dermatitis include M. furfur (formerly Pityrosporum ovale), M. globosa, M. restricta, M. sympodialis, and M.

[3][18][19] Several bacteria, including Propionibacterium species and Staphylococcus aureus, have been shown to have some level of interaction with seborrhoeic dermatitis, though their exact impact is not known.

Those with immunodeficiency (especially infection with HIV) and with neurological disorders that may impact immune system function such as Parkinson's disease (for which the condition is an autonomic sign) and stroke are particularly prone to it.

Additionally, a fungal culture of the affected skin may be taken to attempt to grow and identify the causative organism.

[11] Seborrhoeic dermatitis can look similar to other skin conditions that share its characteristic dry, flaky, scaly, and inflamed appearance but have different causes and treatments.

[3][1] Treatments must take into consideration potential side effects, especially with long-term use given the chronic nature of seborrhoeic dermatitis.

[neutrality is disputed] Initial therapy is usually a topical preparation with an agreeable side effect profile.

[10] Systemic therapy with oral antifungals including itraconazole, fluconazole, ketoconazole is effective, but adverse side effects have been documented for fluconazole and ketoconazole, with the latter not recommended for use, while itraconazole, with its good safety profile, is the most commonly prescribed.

[11][additional citation(s) needed] There is also evidence for the effectiveness of topical calcineurin inhibitors like tacrolimus and pimecrolimus as well as lithium salt therapy.

[25] Calcineurin inhibitors were also effective in reducing growth of Malassezia, offering two routes by which they may treat seborrhoeic dermatitis.

[11] Oral immunosuppressive treatment, such as with prednisone, has been used in short courses for seborrhoeic dermatitis, as a last resort due to its potential side effects.

[8][24] 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.

[31] 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.

[12] Seborrhoeic dermatitis is common in people with alcoholism, between 7 and 11 percent, which is twice the normal expected occurrence.