Vitamin A is believed by many to promote healthy skin in general.  As far as skin conditions go, it seems to be taken more commonly to treat acne.  Accutane is based on a derivative of Vitamin A.

Vitamin A helps your body resist psoriasis the same way that being healthy in general helps your body resist this condition.

Researchers tend to agree that psoriasis is related to misbehaving T-cells, thus, since vitamin A promotes healthy T-Cell activity, it may help to suppress psoriasis.  Vitamin A promotes effective body regeneration and discourages abnormal cell development.

It is possible to take too much vitamin A, so consult your doctor if you have any questions about what is right amount.  Consuming excessive amounts of vitamin A will cause it to store up in the body, eventually becoming toxic.

Vitamin A should be taken with other supplements since it needs the presence of other vitamins and minerals to work effectively.  In particular, be sure you are also taking it vitamin E, zinc and eating protein.

Side effects of taking too much vitamin A include hair loss, jaundice, nausea, blurred vision and decreased mental capacities.