Lyme disease can cause olfactory [smell] hallucinations -- I have had them. The ENT (ear/nose/throat) MD I saw didn't know what it was, but my Lyme dr did. They come and go.
However, if you don't have any of the other signs or symptoms of Lyme, then I would think the likelihood that you have Lyme is low. However, I'm not a doctor, so can't say for sure.
The Mayo Clinic website says:
"Many people are sensitive to certain smells, but in an olfactory hallucination (phantosmia), 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 and usually can't be masked by food.
"Phantosmia most often occurs as a result of a head injury or upper respiratory infection. It can also be caused by temporal lobe seizures, sinusitis, brain tumors, migraine, Parkinson's disease and stroke. ..."
So the simplest answer might be, as your MD said, a sinus infection, which would be treated with antibiotics.
(Interesting that the Mayo Clinic website doesn't mention Lyme as a possible cause. Oh well.)
Many thanks for your comments, most helpful.
bill1988 (Ramsgate, Kent, UK.)
I'd consult a. Gastro. Dr. Bc they could tell you a lot more