Q: I sense an odor within my nose; it smells like a dirty ash tray. I use CPAP for sleep apnea. Could this be the cause or could the odor be from a sinus infection?

A: Using CPAP (Continuous Positive Airway Pressure) for sleep apnea can lead to nasal dryness and crusting and sometimes an abnormal odor. The humidifier on the CPAP machine helps, but is not always enough. Performing nasal irrigation to clean out the nose in the morning may alleviate your symptoms.

However, multiple causes of abnormal smell in the nose are possible. The most common causes are nasal or sinus infections.

Less common causes include these:

  • Dental problems
  • Head injury
  • Chemical exposure
  • Vitamin deficiency
  • Tumors of the nose, nasopharynx (uppermost part of the pharynx) or sinuses
  • Certain medications
  • Partial complex seizures (a type of epileptic seizure)

If nasal irrigation to clean out your nose does not take the smell away, call your doctor's office for advice and to arrange an appointment. Your doctor might refer you to an Ear, Nose and Throat specialist if the problem persists.

David Vernick, M.D., is assistant clinical professor of otology and laryngology at Harvard Medical School and interim chief of the Division of Otology and Laryngology at Beth Israel Deaconess Medical Center.