If you haven’t had a contact allergen patch test yet, you should insist on one. It is a PITA because it's 5 days of itching from sticker residue and the allergens themselves. But, if you have allergies, the difference in your skin when actively avoiding them is amazing.

A lot of psoriasis products have common contact allergens: parabens, sulfates, methylisothiazolinone, and propylene glycol. Etc. Etc.