using exfoliators on plaque psoriasis

If you mean a chemical exfoliator along the lines of Veet, I would stongly recommend against it. I used it on healthy skin some years ago, I left it on for a shorter time than recommended and it still caused a massive redness that turned into psoriasis. I have had wax and sugar hair removal over skin that included some psoriasis and it seemed to actually help. The lady who did the wax exfoliating confirmed to me that she has several clients with psoriasis who all say it seems to help their condition.