Seborrheic dermatitis is a chronic condition characterised by patches of red, scaly, itchy skin. It usually presents on areas of the body where there is increased sebum (oil) production; typically the scalp, face and chest. Dandruff is considered a milder form where there is no associated inflammation. The condition is more common in men, and usually develops in adolescence.
Though the exact process driving seborrheic dermatitis is not fully understood the three core features are high sebum production, over-proliferation of Malassezia (a group of normal skin fungi) and inflammation of the skin. Though increased sebum levels do not directly cause the condition, individuals who do not produce sebum due to lack of androgens (male sex hormones) do not develop seborrheic dermatitis. It has also been proposed immune dysregulation plays a role in the disease development similarly to that seen in psoriasis and eczema. The end microscopic process seen in seborrheic dermatitis is hyper-proliferation of skin cells, driven by inflammation leading to the itchy, red, scaly lesions observed.
The three main treatments for seborrheic dermatitis are antifungals, anti-inflammatories and keratolytic. Anti-fungals act by killing the Malassezia fungus present in the skin, it is not fully understood how this helps but topical and systemic (oral) antifungals have been proven to be both effective treatments and preventative therapies. Anti-inflammatories such topical steroids suppress the inflammatory process in the skin, preventing skin-cell proliferation, they are useful as acute treatments but prolonged use can lead to thinning of the skin. Keratolytic treatments breakdown keratin (the protein which gives skin its strength), this leads to skin softening and shedding of the outer layers, this doesn’t address the driving process but helps treat the plaques and reduces itchiness.