The one thing I've noticed is how psoriosis generally attack "where the sun don't shine" if you'll pardon the expression. The scalp can't receive much sun, for example.
I'd be curious to know if there's a decreased incidence of psoriosis in warmer climates.
Additionally to dairy and red meat, contemporary food additives (such a those in junk food), alcohol, citrus, and wheat have all been implicated in psoriosis in some people. Proteins and poisons are the common triggers. The key seems to be to clean yourself out completely.