The purpose of testing smell is to assess for dysfunction of the olfactory (first) cranial nerves.

Testing the sense of smell does not need to be performed routinely; in fact, this test rarely needs to be done. Smell should be tested, however, in patients who have a complaint of a diminished sense of smell, in patients in whom a frontal lobe lesion is suspected or known, or in patients with a history of closed head injury or skull fracture.

Smell receptors in the nasal mucosa send their axons through the cribriform plate to the ipsilateral olfactory bulb, which then sends its axons to the olfactory cortex.