Vitamin A

Also known as a topical retinoid, its mode of action is not entirely understood. However, it does appear to modulate cell proliferation and increase differentiation. It is marketed as being suitable for mild to moderate plaque psoriasis and should not be used on more than 10% of body surface area. Its main side effect appears to be skin irritation; to help counter this two strengths have been developed, 0.05% and 0.1%.

Method of application
A thin layer should be applied to the plaque only and gently rubbed in. It may be advisable to start at the lower strength first before moving onto the higher strength. One small study suggested that using the product as short contact (product was left on for 20 minutes and then washed off with water) leads to less side effects and equal efficacy (Veraldi et al., 2006).