Although the triggers are many (including several prescription medications, physical trauma, alcohol and smoking), most skin problems are in some way linked to the gut.
In this case, psoriasis is often linked with poor digestion of proteins (possibly due to gut inflammation, possibly food allergies, or both), overgrowth of gut flora (dysbiosis), poor liver detoxification, and nutritional deficiencies. Since 80% of your immune system resides in your gut, this makes sense… clean up the gut, and you can limit a large portion of immune system dysfunction.
Another angle involves adrenal support. Two of the hormones produces by the adrenals (cortisol and DHEA) serve (in part) opposite functions from one another – the former favors a breakdown process (catabolism), while the latter favors a build-up process (anabolism). Supporting the adrenals helps to balance this ratio, which is important, since psoriasis is a catabolic (breakdown) process.
Vitamin D is one nutrient in which quite a few of my patients are deficient (even in AZ!), and this will certainly be a part of a psoriasis protocol. Vitamin D is also a great support to the immune system, and other immune calming (but not suppressive) measures may be appropriate too.
And, when necessary, there are also several herbs (and higher dose nutrients) that have similar mechanisms of action to the prescription meds listed above. These may be necessary to control symptoms while the underlying cause(s) are addressed.