I have scalp psoriasis and it's itching,i wanted to know which shampoo i should use,i can't buy the shampoos from the pharmacy they're too expensive?

Tar shampoo: In USA shampoo is not expensive. A bottle lasts many weeks. Tar, salicylic acid, Zinc pyrethione shampoos are available as low-cost generics which often help psoriasis. Plan to shampoo daily, in a shower if possible. Often useful to wet the scalp and anoint it with shampoo an hour before washing. In US these shampoos are in supermarkets. Consider a visit to a dermatologist.