Dithranol (INN) or anthralin (USAN and former BAN) is a hydroxyanthrone, anthracene derivative, and is used in medications applied to the skin of people with psoriasis.

Dithranol has a slower onset of action in controlling psoriasis, typically several weeks, compared to glucocorticoid steroids, but is without the potential for rebound reaction on withdrawal.

It permanently stains clothing fabrics, shower curtains, and other materials such as ceramic sinks the same yellow-brown to purple in color depending on the concentration.

It may cause a local burning sensation and irritation; this may be minimised by careful attention to the details of treatment and only gradually stepping up through the strengths of dithranol formulations.

Anthralin’s effectiveness as an anti-psoriatic agent has also been in part attributed to its abilities to induce lipid peroxidation and reduce levels of endothelial adhesion molecules which are markedly elevated in psoriatic patients.