The exact cause of Psoriasis is unknown, however the triggers for psoriasis include stress, infection, skin wounds, sunburn, candida, excessive alcohol intake and certain prescribed medications. Poor bowel function, obesity, impaired liver function, and incomplete protein digestion are also risk factors for psoriasis and should be addressed as part of your treatment plan. A deficiency of essential fatty acids and the mineral Sulphur has also been implicated. Psoriasis is sometiimes linked with an over active immune disease. The skin cells multiply and this rapid growth causes thickening of the skin.