My dh has severe psoriasis on his back, arms, legs and scalp. He uses Dovenex which is ok but it never really clears it, just soothes it and makes it look less obvious. This is the one of the strongest creams you can get from the doctors, he also has their brand of shampoo. During the years he has tried Aloe Vera, Tar, Chinese Remedies, peanut and coconut oil, etc, etc. Nothing has cured it, it is an uncurable skin disease I'm afraid. He was offered UVB light treatment but the hospital only offered this during working hours and he cannot afford to take the time off every week for six months. But other people he knows says this 'cured' them for up to a year.
It is an awful disease, for their partners too. I have to change the bed sheets more often than I care to, it gets on furniture, chairs, in the bath, everywhere! And whenever I run my fingers through his hair it looks like a snowstorm! Then he wakes me up at night itching, he will itch until he bleeds, which means more sheet changing! Perhaps we should set up a support group for people and their partners with psoriasis as it is a depressing disease. He hates wearing t-shirts or shorts as people do stare and some ask him if he's been burnt or if it is catching. He won't go swimming anymore because other swimmers would avoid him and the pool attendents would have to confirm that it was not contagious.
So you have my every sympathy MandyD. Watching his diet might also help, cutting down on rich and spicy foods, tobacco, alcohol (all the things we like to eat, but which will inflame his psoriasis more). The worst thing is that it runs in the family (his sister and brother have it to lesser degrees) and I am really concerned that dd might get it, it must be awful for girls especially.
Sorry I can't help more.