What is it?
Most cases of dandruff are caused by seborrheic dermatitis -- 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.
However, in some cases, dandruff may be caused by psoriasis.
What causes it?
The exact cause of dandruff (or seborrheic dermatitis) is not known. People who suffer from dandruff typically show higher levels of skin oil production, and an increased presence of skin fungi (which triggers skin inflammation leading to itchy, flaky skin). Typical treatments therefore aim to reduce one or both of these.
How to treat it?
The main treatments for seborrheic dermatitis are:
Anti-fungal creams: which act by killing the fungus present in the skin.
Anti-inflammatory creams, such as topical steroids, suppress the inflammatory process in the skin, preventing skin-cell proliferation. They are useful in severe cases but prolonged use can lead to thinning of the skin.
Keratolytic treatments break down keratin (the protein which gives skin its strength). This leads to a softening of the skin and the shedding of its outer layers. While this does not address the root cause, it can help to reduce itchiness.
Reducing sebum production: though there is no licensed treatment that focuses specifically on this issue, ketoconazole an antifungal has been proven to reduce sebum production through acting as an anti-androgen (medications that lower male sex hormones).