Some loss of sensitivity to smells — also known as anosmia — is normal as we get older, but there may be another explanation. The ability to smell depends on a healthy lining of the nasal cavity, open nasal passageways, and normal function of the olfactory (smell) nerves. A problem with one or more of these can lead to loss of smell. The most common causes are nasal problems, like nasal polyps, blocked sinuses, and seasonal allergies. These can be detected by a routine examination, although you may need to see an ear, nose, and throat specialist for a more extensive exam.

Another possibility is a problem with part of the nervous system responsible for smell. Some studies have suggested that loss of smell could be an early sign of a neurodegenerative disease, such as Alzheimer's or Parkinson's disease. However, a recent study of 1,430 people (average age about 80) showed that 76% of people with anosmia had normal cognitive function at the study's end.

If you notice a major change in your sensation of smell, be sure to mention it to your doctor at your next visit.