Can you smell a rose?
How do you smell?
A smell begins when a molecule -- say, from a flower -- stimulates the olfactory nerve cells, part of the olfactory cranial nerve, found high up in the nose. These nerve cells then send information to the brain, which identifies the specific smell.
Why you lose the sense of smell?
There are over 100 reasons why people can lose their sense of smell. However, most people lose it from sinusitis, after viral infections, traumas, or tumors. It can often be of idiopathic (unknown) origin. When you catch a severe cold, your nose stuffs up; you can't smell anything, and food tastes funny. Fortunately, most people regain their sense of smell once the cold runs its course. But for others, the complete (anosmia) or partial (hyposmia) loss of the sense of smell is permanent.
Cranial nerves control how things work in our head and neck -- such as the nerves that allow us to speak by using our vocal cords, control our facial motion, hear and smell. A variety of viruses can attack the cranial nerves related to smell or the mucosal tissue surrounding those nerves. Common coronavirus infections by rhinoviruses and influenza viruses lead to colds and upper respiratory illnesses. COVID-19 is one type of disease caused by a coronavirus (SARS-CoV2). They cause inflammation in and around the nerves, which cannot function properly. This leads to the loss or dysfunction of smell. It can happen to anyone: young and old, healthy, and sick.
Smell loss can be one of the earliest signs of a COVID-19 infection. It can sometimes be the only sign. Or it can present after other symptoms. Although it may not affect every patient with COVID-19, loss of smell and taste is associated with the disease. In some countries, including France, they've used this as a triage mechanism. People need to know that altered smell can be due to the COVID-19 disease process, so they aren't going about their lives like normal and spreading the virus.
The pandemic also might impact how we treat patients with olfactory dysfunction in general. When someone has a viral-induced inflammation of the nerve, they are sometimes treated with steroids to decrease the inflammation. But treating all COVID-19 patients with steroids might be a bad idea because of its effect on the inflammatory processes in their heart and lungs.
For those who lose the ability to smell after trauma, postviral infection, or when we don't know why it happened, olfactory training can be used, a straightforward protocol that patients can do at home. The patients smell several essential oils ( rose, eucalyptus, clove, and lemon) in a structured way twice a day, every day, over a long time. The oils stimulate different types of olfactory receptor cells in the nose. It is useful in 30 to 50 percent of patients. Researchers are trying to find out if both stem cells and neurostimulation can work. The olfactory nerve has an inherent ability to regenerate. Researchers are taking advantage of this fact and switch on those regenerative cells.
Bottomline
The treatment depends on the reason for the loss and may include surgery or medications.
If you lose your sense of smell and it isn't coming back after all the other symptoms have gone away, seek care as soon as possible. If you wait too long, your options dwindle. Interventions, including olfactory training and medications, are more effective when you get early treatment.
If you lose your sense of smell or taste during this pandemic and don't have any other symptoms, contact your doctor. The doctor can decide whether you require COVID-19 testing and self-isolation to avoid being a vector of the virus in your family or community.
Some interesting facts
Humans possess around 12 million olfactory receptor cells that can detect approximately 10,000 odors. Dogs, on the other hand, have anything from 100 to 200 million-plus receptor cells, depending on the breed. The bloodhound is thought to have more receptor cells than any other dog (as many as 300 million) and can detect 40,000 different odors! The higher concentration of an odor, the stronger the signal sent by the receptor cells to the olfactory bulb.
References:
Published 12/11/2020
Dr. Amar Singh, MD, and Dr. Poonam Singh, MD, are board-certified by the American Board of Internal Medicine and American Board of Obesity Medicine. They specialize in preventing, treating, and reversing chronic diseases using an evidence-based holistic approach. They are specifically interested in weight management, hormone re-balancing, and longevity. The American College of Physicians has recognized them as Fellows, FACP, for their excellence and contributions made to both medicine and the broader community. They enjoy teaching, volunteering, and advocating for their patients. Their mission is to share simple, effective, and proven strategies that lead to meaningful, sustainable, and long-lasting well-being.
