Phantosmia

Phantosmia is the phenomenon of smelling odors that aren't really present. The most common odors are unpleasant smells such as rotting flesh, vomit, feces, smoke etc. Phantosmia often results from damage to the nervous tissue in the olfactory system. The damage can be caused by viral infection, brain tumor, trauma, surgery, and possibly exposure to toxins or drugs. It can also be induced by epilepsy affecting the olfactory cortex. It is also thought the condition can have psychiatric origins.