Tablets named 'methotrexate' do help Psoriasis, and have been used in treatment. These tables are used in higher doses to treat some cancers and leukaemias, and as they are very strong, they are ordered only for people with bad and stubborn Psoriasis.

Care is taken that ulcers do not develop in the mouth, and that blood formation is not affected in early stages after treatment, and that no liver damage occurs later in treatment. They must not be given during pregnancy.

More recently, tablets which make the skin sensitive to sunlight, names 'psoralens' have been used, either with sun exposure or with ultra-violet light in the 'A' spectrum. This has come to be know as PUVA.

Again, this treatment is only suitable for some people with sever and stubborn Psoriasis, and the long range good and bad effects of the treatment have yet to be determined.