The loss of the sense of smell is the second most common presenting symptom of COVID. It occurs in 65% of patients. Fatigue occurs in 68% and headache, in 43%. Severe loss of the sense of smell was still present in 11% of patients after one month and in 7% after two months.
A study published by French researchers in Neurology, reports on the likely cause of the loss of smell. They obtained MRI scans in 20 patients with COVID-related loss of smell. Nineteen out of 20 had complete occlusion of the olfactory clefts due to swelling. The clefts are two narrow vertical passages at the upper part of the nasal cavity. They are lined with the olfactory epithelium containing olfactory receptors. They found a correlation between the degree of olfactory impairment and the degree of occlusion of the olfactory cleft.
The logical conclusion is that treating the swelling could help improve the sense of smell and possibly reduce the chance of permanent impairment. In the discussion section of the paper, the authors state that most treatments for virus-induced inflammation do not work. However, the only reference they provide is a study of 34 patients who were given the equivalent of 10-15 mg of prednisone. The majority of published trials of oral steroids for chronic sinusitis used 30 to 60 mg. Sudden hearing loss and Bell’s palsy are very different conditions but are also thought to involve swelling and inflammation and are treated with a short course of prednisone, typically 60 mg a day.
One of the articles cited above was accompanied by an editorial that recommends using a steroid nasal spray. This sounds reasonable for milder cases, but if I were to completely lose my sense of smell, I would take at least 30 mg of prednisone.
Persistent loss of smell can be a devastating condition. According to Healthline, the loss of the sense of smell can lead to
1. an inability to taste food, which can lead to eating too much or too little
2. an inability to smell spoiled food, which can lead to food poisoning
3. increased danger in the event of a fire if you cannot smell smoke
4. losing the ability to recall smell-related memories
5. loss of intimacy due to the inability to smell perfume or pheromones
6. losing the ability to detect chemicals or other dangerous odors in your home
7. lack of empathy from family, friends, or doctors
8. inability to detect body odors
9. mood disorders such as depression
10. lack of interest in social situations, which might include being unable to enjoy the food at a social gathering
