Has anyone ever heard of a highly over-sensitive sense of smell with dementia?

Phantosmia is a form of olfactory hallucination. While most olfactory hallucinations are caused by a misinterpretation of a physical stimulus, such as in the case of parosmia, phantosmia is the perception of a smell in the complete absence of any physical odors. The odor can range from pleasant to disgusting. Although the causes of phantosmia are uncertain, it often occurs with neurological and psychological disorders such as schizophrenia, mood disorders, Parkinsons disease, epilepsy, neuroblastoma, and frequent migraines.

Once your mom points out what she's smelling can you then smell it too? If you can't, I'm wondering if she actually is smelling things that aren't there, that she might be imagining it.

That's interesting. You didn't say how old your mother is, but I'm assuming she isn't pregnant. (Joke.) A heightened sense of smell is common with pregnancy. Is she on any new medications? Does she have epilepsy or migraine headaches? Smelling strange odors sometimes comes along with both of those conditions.

What kind of smells is she reporting? Rotten eggs? Oranges? Or something else? You might mention it to her doctor, in case something neurological is going on. (I know, "something neurological" is pretty vague.)

From what you said in another post about your mother being anxious, maybe is has something to do with her anxiety, especially if she's reporting the smell of smoke, or spoiled food.