Psoriasis is an autoimmune disease.Basically your immunity is acting against your own skin cells at the places where you have the psoriatic patch. There is no permanent cure to it.Hoever you can get rid of your present patches with ointments (allopathic). But after that you have to maintain it regularly by using good emolients to keep your skin hydrated always.Dryness can induce itching n new patches. You wont have to take medicines forever but yes whenever you have a new patch develeoping you have to again start with the treatemtn of ointments at early stage so it will not worsen. Also if once present patches are treated then not necessary you will get it again immediately.Some may get it immediately again while some patients dont get it for next 10-15 years.So all depends on how your body type is and the way to maintain it later.