This is a medication used to relieve itching, which can be a problem for some people with psoriasis. It works by blocking the release of histamine. Histamine, when released in excess, is the principal cause of both inflammation and allergic symptoms. By suppressing or reducing histamine you can reduce the itch and the potential damage to the skin from scratching; this mechanical damage keeps the inflammatory process going and can increase the potential for localised skin infections. Itching can disturb sleep and lower self-esteem.