BMJ Group Medical Reference
There's some good research to show that using strong steroid creams can improve your psoriasis. But you can use steroid creams only for short periods of time, because of side effects. 
Your doctor may prescribe a steroid cream for a few days or a few weeks. Steroid creams work by making your skin less inflamed. You can buy low-dose steroid creams from a pharmacy. But it's best to talk to your doctor about this treatment. They can give you advice on using steroids and prescribe stronger creams if you need them. You'll need a prescription from your doctor for stronger creams.
Brand names for the stronger creams include Betnovate, Dioderm, and Locoid. A newer treatment, Dovobet, combines a strong steroid with a vitamin D treatment (calcipotriol). It is available as a gel and ointment.
One summary of the research showed that strong steroid creams can improve psoriasis in the short term.  We also found one study that showed applying a steroid cream once a week can help to keep an area of your skin clear.  Also, using a steroid cream together with another type of cream or ointment (for example, a vitamin D cream or tazarotene) can work better than applying either treatment on its own.
You probably shouldn't use low-dose steroid creams for longer than a month at a time. And you probably shouldn't use strong steroids regularly for more than seven days. That's because steroid creams have side effects. They can make your skin thinner. That's more likely to happen if you use a stronger cream and if you wear a dressing over a treated area of your skin. 
If you use a steroid cream continuously, your body won't produce so much of its own natural steroids. So your psoriasis might flare up again when you stop using the cream.
Some people worry that steroid creams may become less effective the longer you use them. But we couldn't find any evidence to show this. 
For references related to Psoriasis click here