Causes of Loss of Smell and Taste
Olfactory disorders have many causes, and a specialist such as an ear, nose, and throat (ENT) doctor is typically necessary to sort out the root cause. As a rule, if you have lost your sense of smell for more than two weeks, you should seek a physician to determine the cause.
The most common cause for loss of smell and taste is simply nasal obstruction, such as from congestion due to a cold or bad allergies. Long-standing nasal obstruction from something like nasal polyps or severe nasal septal deflections can also be a cause of obstruction.
Either way, if your nose is blocked, you won’t be able to get those aromatic particles to reach the top of your nose to stimulate the nerves of olfaction.
The second most common cause is damage from an infection, especially viruses. Viruses are known to damage all kinds of nerves (especially cranial nerves), including the nerves in the nose used for smell.
After a viral infection, sense of smell typically returns within two weeks, although recovery can vary from weeks to months. Permanent damage to the nerves may also occur.
The coronavirus that has led to the COVID-19 pandemic has caused an increase in patients losing their sense of smell and taste. Like any virus, the coronavirus attaches to the nasal receptors (specifically the ACE2 receptor) and causes damage.
In our clinic, we’ve found that recovery is often extended to several months post-COVID and is often associated with a temporary phase of parosmia, where your sense of smell or taste changes (oftentimes for the worse).
Less common causes of olfactory disorders include head trauma (concussions), various nasal and brain masses and tumors, neurodegenerative disorders (dementia), as well as toxin and medicine side effects. In some patients, the cause may simply be unknown.
[Related: What Can Cause Loss of Smell?]