In conditions called parosmia and phantosmia , people smell odors that aren't there. (Apparently, parosmia means that one odor is perceived as another odor. Phantosmia seems to be where a person smells an odor even though there's nothing to smell.) I'm not a doctor, but I think it makes sense to check with a primary care physician or an ear-nose-and-throat specialist. You could also look at this Yahoo health group .
