Dithranol with salicylic acid and zinc oxide

How it works

Dithranol inhibits keratinocyte proliferation and has antiproliferative and anti-inflammatory effects, while salicylic acid acts as a keratolytic to remove scale and zinc oxide provides a soothing, protective barrier and stabilises the preparation.

Prescribing in practice

• Dithranol stains skin, hair, clothing, bedding and bathroom surfaces and is irritant, so it must be applied accurately to plaques and kept off normal skin, the face and flexures.
• It should be avoided on acute, inflamed or pustular psoriasis and washed off carefully to limit a chemical burn-like reaction.
• Salicylic acid can be absorbed if applied over large areas or broken skin, so use is restricted in such circumstances.

Monitoring

Monitor the treated plaques and surrounding skin for irritation and staining at each review and adjust contact time accordingly.

Counselling the patient

• Apply only to the thickened patches, wear gloves, and wash hands thoroughly afterwards.
• Expect temporary brown-purple staining of the skin and permanent staining of fabrics and surfaces, so protect clothing and the bath.
• Wash the paste off as directed and stop if the skin becomes very sore.

Evidence & guidelines

Dithranol-based topical regimens are long-established treatments for chronic plaque psoriasis and are recognised in NICE psoriasis guidance.