The SARS-CoV-2 virus that causes COVID-19 is an airborne organism, meaning that breathing in viral particles from infected people nearby is the main way it spreads. The virus can enter your body through your nose, eyes, or mouth, but since most of the air that you breathe in enters through your nose, your nostrils are the primary entryways for transmission. Stopping the virus there would certainly be an efficient way to help prevent infection.
Unfortunately, there is no nasal spray available in the United States that has been shown to protect against COVID-19, either by interfering with its transmission or by reducing the severity of disease. None of the over-the-counter nasal sprays available for allergies or asthma have any effect on COVID-19, but there are other formulas being developed, including therapies based on nitric oxide and carrageenan. Some of these are being tested in laboratories, and a few are even in clinical trials in humans.
Nitric oxide, or NO, is made naturally in the body and serves an important function as a vasodilator that improves circulation. It also has anti-viral properties, and we’ve known for more than a decade that it inhibits the replication of the first identified SARS coronaviruses. In 2020, laboratory tests showed it to be effective at stopping replication of the novel coronavirus, SARS-CoV-2.
Nitric oxide is currently being tested in humans to determine its effectiveness at preventing transmission of SARS-CoV-2, or to reduce the severity of illness by reducing the viral load in those who become infected. A nitric oxide nasal spray was recently granted an emergency use authorization in Israel and is now being evaluated in a clinical trial in Canada. Other clinical trials are beginning in other countries.
In March 2020, the FDA granted emergency use authorization for inhaled nitric oxide as a treatment for patients with severe illness from COVID-19. Its usefulness as a preventive measure is still unproven, however, and further clinical trials are needed to provide more information about its effectiveness as a treatment.
Carrageenan is a substance made from marine algae that has been shown in laboratory testing to be active against a wide range of viruses, including influenza, human papillomavirus, and many others.
A clinical trial now underway in the UK is testing the effectiveness of iota-carrageenan nasal and throat spray in preventing COVID-19 illness, or reducing the severity of symptoms, in healthcare professionals. Results of an unpublished clinical trial performed in Argentina suggest that health care workers treated with a combination of ivermectin drops and iota-carrageenan nasal spray were less likely to develop COVID-19 than untreated colleagues, and those who did get infected were less severely ill than those in the control group. I’ve written about ivermectin previously on this site.
There may be potential for these nasal sprays, but right now the best ways to keep the novel coronavirus out of your nostrils are to wear a mask and keep your distance from others who may be exhaling particles.
Andrew Weil, M.D.
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