What Causes Lack Of Sense Of Smell And Taste?

My Mom hasn't been able to smell or taste for the past couple of weeks. Weeks ago she was ill and on a nasal spray and a decongestant. Now she is better but she still cannot taste or smell. Her doctor put her on a steroid and zinc for 15 days, I believe she is at the 9th day, but she still can't taste or smell. She is very worried and she soesn't know what to do next. Mom is 70 years old.