I've been smelling cigarette smoke when none exists. What is the cause? What kind of doc. Should I see? I do have seasonal allergies from aug-nov.

Smell hallucination? Olfactory hallucinations can result from head injury, upper respiratory infection (uri), sinusitis, migraine. Phantosmia can also occur with temporal lobe seizures, brain tumor or other neurological disorder. Consult with your doctor or allergist to make sure any allergy symptoms are optimally controlled. Saline nasal spray or rinse can be quite helpful. If the smell persists, see a neurologist.
Go to ENT. Go to an ENT for this "paraosmia" so he can rule out pathology in th olfactory tracts or brain.