Phantosmia (phantom smell), also called an olfactory hallucination or a phantom odor, is smelling an odor that is not actually there. It can occur in one nostril or both. Unpleasant phantosmia, cacosmia, is more common and is often described as smelling something that is burned, foul, spoiled, or rotten.

Why can I smell something burning?

It's also called olfactory hallucination. The smells may always be present, or may come and go. They may be temporary or last for a long time. Smelling smoky or burning smells — including burnt toast — is a common type of phantosmia.

Why can I always smell smoke?

The term for this type of olfactory hallucination is dysosmia. Common causes of dysosmia are head and nose injury, viral damage to the smell system after a bad cold, chronic recurrent sinus infections and allergy, and nasal polyps and tumors. The brain is usually not the source.