How common are olfactory hallucinations in complicated migraines?

Rare: Although this has been reported, it is rare.

Uncommon but happens: Olfactory hallucinations (“phantosmias”) are seen occasionally in people with complicated migraines. There have been limited reports of this symptom in patients with migraines with one study showing less than 1% of patients at a headache center having olfactory hallucinations. As uncommon as they are, they have been observed.