What medicines could be causing my husband to lose his sense of taste and smell? he is on trazadone, blood pressure med., niacine, fish oil.

Not sure: I would eliminate all unnecessary medications and see a physician.

Head injury?: Has your husband had a head injury -- maybe fallen and hit his head? Sometimes the tiny olfactory nerves from nose to brain can be damaged, resulting in poor sense of smell. Since ability to smell impacts one's ability to taste, sense of taste could be damaged also. There are other possible causes as well . . . Please encourage your husband to talk to his doctor about this.