Treatments in the test phase
In the meantime, numerous treatment options are being explored, often in small clinical trials. However, these therapies are still in the early stages, so that most scientists only recommend smell training for the time being. Patients are given samples of strong-smelling substances that they are asked to smell and try to identify in order to encourage the transmission of odor signals. However, this method only seems to work for people with partial smell loss, says Reed. Valentina Parma adds that this means that she is helping about a third of people who are struggling with a chemosensory disorder after Covid-19.
To find treatments for everyone else, many teams are researching the use of anti-inflammatory steroids. It is known that Covid-19 triggers extensive inflammatory reactions, which may play a role in the disturbance of the sense of smell. So in theory steroids could help, but in practice the results so far have been disappointing. For example, in a 2021 study, 100 people with post-Covid anosmia were given smell training. Fifty of them also received a nasal spray containing the steroid mometasone furoate, while the other 50 subjects served as controls. There was no significant difference between the two groups.
Platelet-rich plasma is considered another therapeutic option. It is made from the patient’s own blood and is rich in biochemicals that may promote healing. A pilot study published in 2020 looked at seven patients who had platelet-rich plasma injected into their noses. Five of them improved after three months. A preliminary publication published in February of this year also found that platelet-rich plasma increased odor sensitivity in 56 people. But these are “really low numbers,” said Carl Philpott, a nasal and sinus specialist at the University of East Anglia in Norwich, England. A US team has now started a larger study.
Unlike the Covid-19 vaccines, which have been developed and tested at an unprecedented rate due to massive government support, treatments for the chemosensory disorders that occur after Covid illness have been slow to progress. Philpott is in the early stages of a small study on vitamin A, which previous experiments suggest could help with other forms of smell loss as well. “The study will take the rest of this year, and it will probably take us until the middle of next year to analyze the data and produce a report,” says Philpott. “If we see a positive impact, our next task will be to apply for additional funding to conduct a more comprehensive study.”