More than four years after SARS-CoV-2 made its global debut, the US Food and Drug Administration is still working to clear out the bogus and unproven products that flooded the market claiming to prevent, treat, and cure COVID-19.

The latest example is an alcohol-based sanitizer meant to be smeared inside the nostrils. According to its maker, the rub can protect you from becoming infected with SARS-CoV-2 and other nasty germs, like MRSA, and that protection lasts up to 12 hours after each swabbing. That all sounds great, but according to the FDA, none of it is proven. In a warning letter released Tuesday, the agency determined the sanitizer, called Nozin, is an unapproved new drug and misbranded.

While ethyl alcohol is used in common topical antiseptics, like hand sanitizers, the FDA does not generally consider it safe for inside the nostrils—and the agency is unaware of any high-quality clinical data showing that Nozin is safe, let alone effective. The FDA also noted that, for general over-the-counter topical antiseptics, calling out specific pathogens it can fight off—like SARS-CoV-2 and MRSA—is not allowed under agency rules without further FDA review. Making claims about protection duration is also not allowed.

The FDA's warning letter is nothing to sneeze at; the letter threatens seizure and injunction for failing to adequately respond.

Nozin's maker, Maryland-based Global Life Technologies Corp., did not immediately respond to a request for comment from Ars. On its website, the company touts its product's effectiveness with a link to a published study from 2014, indicating that use of Nozin lowered the colonization levels of S. aureus and other bacteria in the noses of 20 healthy health care workers. The study did not address protection from infection or carriage of any viruses. The company also lists unpublished studies indicating that the product can kill bacteria in laboratory conditions, does not irritate skin, and lowered bacterial growth in the noses of 30 people over a 12-hour period.

This is far from the first dubious, nasal-based COVID product the FDA has called out. There was the Corona-cure nasal spray of 2020, and the Halodine and NanoBio Protect nasal antiseptics of 2021. That year, the Federal Trade Commission sued a company called Xlear over allegedly false claims that its nasal spray can prevent and treat COVID-19. At least two more nasal spray makers received FDA warning letters in 2022.

To date, the FDA has not approved any nasal sprays to prevent or treat COVID-19, and the scant data on their efficacy remains inconclusive. But there are still plenty of such products for sale online. Most, like Nozin, claim to work by killing bacteria and viruses directly. One product, a nitric oxide nasal spray called Sanotize, is currently in a Phase III clinical trial to test whether it can prevent SARS-CoV-2 infections. Others claim to work by coating the nasal passage with the gelling agent iota-carrageenan to provide a barrier to viral entry. A pilot clinical trial of 400 health care workers in Argentina published in 2021 found that the use of an iota-carrageenan nasal spray led to a 4 percent absolute risk reduction in SARS-CoV-2 infection.