Vitamin B2 brought my sense of smell back. I wasn't looking for it to do so, but I took my first one (100 mg) and the next morning I could smell stuff that I hadn't apparently in a year or two.

Since then I spent about 6 months taking B2 every day. I found that it amplified my pains as well as sense of smell. I have been able to taper down to nothing now and still have my sense of pain and sense of smell.