Medicines are best, but you can do some things to treat your psoriasis without a prescription. Apply thick lotions or creams, then seal in the moisture with ointments like petroleum jelly (Vaseline), shortening, or olive oil. Do it regularly. Dry skin makes the irritation and itchiness worse. Don't go too thick during hot, sticky summer months. Sweat mixed with thick creams can make your psoriasis worse.
Right after your bath or shower, pat yourself somewhat dry with a towel -- don't rub -- and put the creams on to seal in water. Before you hop into bed, wrap your skin with a bandage or plastic wrap. In the morning, wash the area gently. Over time, this can reduce scaling.