Studies have shown and proved that Candida is one of the psoriasis causes (1). If Candida is your psoriasis causes I would recommend bring changes to your diet and lifestyle. First, I would recommend you avoid foods that contain sugars, grains and alcohol as they will only make matters worst due to feeding the Candida further. Instead focus on consuming leafy green vegetables. Along with that also take coconut oil. Coconut oil contains 3 different fatty acids (Caprylic Acid, Capric Acid, Lauric Acid) that have each been found to be effective against the Candida yeast.Caprylic acid in particular is a popular and effective antifungal, which you can buy in supplement form.
http://www.candida-albicans-cure.com/psoriasis-causes.html#R1 - (1)