When a person smells thing that are not there the condition is called Phantosmia.
Phantosmia causes you to smell things that are not really there in your environment.
An olfactory hallucination (phantosmia) makes you detect smells that aren't really present in your environment.
The odors detected in phantosmia vary from person to person and may be foul or pleasant.
They can occur in one or both nostrils.
The phantom smell may seem to always be present or it may come and go.
Phantosmia is not usually a cause for concern, and it often clears up by itself.
It can also be a symptom of a more serious condition, so people experiencing phantom smells should see their doctor to check for underlying conditions or complications.
Experiencing occasional phantom smells is normal and usually goes away on its own in time.
When hallucinations of this type do not seem to go away or when they keep coming back, it can be very upsetting and can disrupt an individual's quality of life.
Brief episodes of phantom smells or phantosmia — smelling something that's not there — can be triggered by temporal lobe seizures, epilepsy, or head trauma.
Phantosmia is also associated with Alzheimer's and occasionally with the onset of a migraine.
Some ways to get rid of phantom smells are.
Rinsing your nasal passages with a saline solution (for example, with a neti pot)
Using oxymetazoline spray to reduce nasal congestion.
Using an anesthetic spray to numb your olfactory nerve cells.