Dropsy!

I'm afraid that when a fish reaches the stage of sticking out scales, there is usually nothing that can be done. Dropsy isn't a disease itself, it is a symptom of several diseases. Once the underlying disease reaches the stage of causing kidney failure, the fluids inside the fish build up and the scales stick out - dropsy.
In order to try a treatment, the underlying disease needs to be identified. A bacterial infection can be treated, but if you are in the UK we can't buy antibiotics without a vet's prescription and the only medications available to us aren't very strong. A viral infection can't be treated at all. Protozoan or other internal parasites can be treated if you know that's what the cause is. But one the fish goes into kidney failure there is usually little that can be done.
Dropsy is only infectious if the disease that caused the dropsy is infectious.

Do you have a quarantine tank? If you do, you could try eSHa 2000, which claims to treat dropsy. Other than that, I'm afraid there is nothing that can be done. I'm sorry.