Q: I lost my sense of smell after a bad cold and it hasn't come back. Will it ever return?
A: Possibly, but you should consult your health care provider to make sure this wasn't caused by something other than the cold. Total loss of smell (anosmia) or partial loss (hyposmia) often occurs during or after a bad cold or other upper respiratory tract infection (URI). Both conditions fall under what's called postviral olfactory dysfunction (PVOD) or post-infectious olfactory loss. URI-related anosmia or hyposmia is usually temporary, but in some cases the condition is permanent.
Other possible causes of loss of smell besides URI viruses include chronic sinus problems, allergies, nasal polyps, head injury, medications, and exposure to certain airborne chemicals. These generally cause loss of smell by damaging olfactory receptors, nerve fibers, and surrounding cells in the rear of the nose or by blocking the flow of odor molecules through nasal passages. Aging itself is associated with gradual impairment of the sense of smell.
Until the FDA issued warnings about such cold remedies in 2009, zinc products applied directly into the nose, such as gels and swabs, caused anosmia in hundreds of people, leading to many lawsuits.
About one-third of people with PVOD regain their sense of smell without treatment, usually in six to 12 months. Younger people are more likely to recover than older people.
In cases that don't improve on their own, early treatment improves the odds of recovery. Treatments for anosmia include steroid drugs, with oral steroids usually working better than topical, especially if started early on. The herb ginkgo biloba, taken with or without steroids, may help treat PVOD, according to a small Korean study in JAMA Otolaryngology—Head and Neck Surgery in 2009.
At least one small 2016 Chinese study suggested that acupuncture may help treat PVOD. But since the comparison group got no treatment, rather than sham acupuncture, a placebo effect cannot be ruled out.
Olfactory training, in which you sniff different essential oils for several months, may be worth a try. An analysis in the International Forum of Allergy and Rhinology in 2015 looked at 10 studies on such training and concluded that it can help with olfactory loss. Some clinics, medical centers, and private physicians, especially those who specialize in nasal conditions, offer olfactory training.
Also see Making Sense of Smell.