A change in smelling ability (the sense of “olfaction”) is known as anosmia or parosmia. It is of course very common with the cold, flu, or sinusitis, but can be a real burden if the loss of smell sticks around afterwards.
The most common reason for anosmia is swelling in the top of the nasal cavity where the smell organs live. Occasionally nasal polyps or even a tumor can cause the blockage of the sensory tissue.
For persistent loss of smell (anosmia), or change in smell (parosmia) an evaluation by an otolaryngologist is important to examine for inflammation or blockage near the cribiform plate, the thin bone at the top of the nasal cavity. The evaluation may consist of a standardized smell test and a careful look at the internal nasal structures. Sometimes an MRI or CAT scan may even be recommended.
Treatment of smell disorders is difficult. Often a trial of a potent steroid is attempted, which can help reduce nasal inflammation and even reduce any swelling that may be acting on the smelling nerve itself. Also, high doses of ginko biloba can be attempted under a doctor’s supervision (high dose ginko has numerous interactions with other medications). Of course sometimes surgery may be needed to help clear nasal polyps or a stubborn sinus infection. Finally some centers even offer Olfactory Retraining, a sort of physical therapy for the sense of smell.