Loss of sense of smell (anosmia): What causes it?

We recently learned that our 6-year-old son has no sense of smell. What causes this?

- No name / No state given

Mayo Clinic pediatrician Jay Hoecker, M.D., and colleagues answer select questions from readers.

Answer

Loss of ability to smell (anosmia) can be temporary or permanent depending on the cause. Temporary anosmia is common with colds, sinus infections (sinusitis) and nasal allergies. Other potential causes of anosmia include:

Enlarged adenoids
Nasal polyps
Exposure to tobacco smoke
A side effect of medication
Trauma to the face and nasal structures
Tumors, such as neuroblastomas, meningiomas, frontal globe gliomas and pituitary gland tumors

Rarely, babies are born without a sense of smell (congenital anosmia), such as in Kallmann syndrome, an uncommon inherited disorder. In some cases, the cause of anosmia can't be determined (idiopathic anosmia).