Dozens of hand sanitizers contain a toxic ingredient. How do you know yours is safe?

The U.S. Food and Drug Administration (FDA) has identified at least 77 hand sanitizers that contain dangerous levels of methanol, a toxic substance that can cause nausea, nerve damage and blindness when absorbed through the skin and death, if ingested.

In June, the FDA issued a warning about nine tainted hand sanitizers made by a company called Eskbiochem, Live Science previously reported, but since then, the agency has flagged dozens of additional products that contain dangerous levels of methanol, also known as wood alcohol, The Washington Post reported. The agency keeps a running list of these sanitizers on its website and notes that the products pose a particular risk to young children, who may accidentally ingest them, and for adults who purposefully drink the products as an alcohol substitute.

But how are so many products becoming tainted with methanol in the first place? Most likely, the surge stems from sloppy manufacturing processes, wherein producers may not properly remove methanol that naturally arises during alcohol distillation, or they may violate FDA guidelines by starting with an already distilled high-methanol solvent as their base, sources told Live Science. (Methanol distillates are a common ingredient in antifreeze and racing fuel.)

And unfortunately, while experts can smell the difference between methanol and ethanol, most consumers won't be able to detect this difference. And "methanol" will not be listed in the ingredients on the bottle. Instead, people should check the FDA's list of recalled sanitizer products to make sure theirs is not on it, and avoid unknown brands, experts told Live Science.

Related: Hand sanitizer sold out? Here's how to make your own.

Methanol can be lethal at fairly low doses: Ingestion of as little as 2 tablespoons (30 milliliters) of methanol can be deadly for a child, and 2 to 8 ounces (60 to 240 milliliters) can be deadly for an adult, Live Science previously reported. Even if only applied to the skin, methanol can be absorbed and cause severe illness and nerve damage, Dr. William Banner, Medical Director of the Oklahoma Center for Poison and Drug Information and a past president of the American Association of Poison Control Centers, told Live Science.

Topical methanol can be particularly dangerous for children, who have a greater ratio of skin surface area to body weight as compared with adults, Banner added. That said, consumers would likely need to apply the product repeatedly (as one does with hand sanitizer) to absorb a dose high enough to become poisoned, he said.

Lessons from distilleries 

Methanol contamination is a problem that distillers appreciate all too well — it's why illicit moonshine and other homemade liquors may be riskier to consume than spirits made by legitimate distilleries.

Alcohol production begins with the fermentation of sugars to produce both methanol and ethanol, the kind of alcohol that's considered fairly safe to drink and one of the best base ingredients for hand sanitizer, Live Science previously reported. Following fermentation, manufacturers boil the alcohols and collect their vapors, allowing them to condense into a concentrated "distillate." But methanol boils at a lower temperature than ethanol and therefore evaporates first in this distillation process. 

When ethanol does begin to boil, at 173.1 degrees Fahrenheit (78.37 degrees Celsius), manufacturers must "cut" the stream of alcohol and swap out their collection container; this ensures that the final product contains primarily ethanol, and the excess methanol gets tossed, Mike Blaum, co-owner and chief distiller of the Blaum Bros. Distilling Co. in Galena, Illinois, told Live Science. After the methanol is removed, the remaining distillate is mostly ethanol, the key ingredient in liquor, along with other compounds that provide flavor. 

A very small amount of methanol does end up in the final beverage, but the dose must be kept below a certain threshold so as not to pose significant health risks, according to a 2001 report in the journal Human and Experimental Toxicology. For example, the FDA caps the maximum permitted level of methyl alcohol in brandy at 0.35%.

While commercial alcohol producers undergo rigorous safety checks to prove they've done this correctly, unregulated moonshine makers do not.

"For us, we really know how to ensure that there's no risk of methanol or any other toxicity," Blaum said. As a well-trained distiller, "you can smell and you can taste the difference" when the ratio of methanol to ethanol becomes too high, he said.  In addition to these sensory cues, distillers monitor the density of the distillate and the temperature of various components within the apparatus that the alcohols flow through. Companies also periodically send distillate samples to labs equipped with gas chromatography–mass spectrometry (GCMS) — a technique used to analyze the ratio of chemicals present within a particular batch, Blaum said.

Related: 7 ways alcohol affects your health 

Manufacturers also make sure their fermentation vats don't become overrun with bacteria that produce extra methanol, Live Science previously reported.

The same quality controls should be applied when producing alcohol for hand sanitizer, as Blaum Bros. and other American distilleries began to do in late March with guidance from the FDA and the Alcohol and Tobacco Tax and Trade Bureau. The distilleries have been directed to follow formulas for hand sanitizer provided by the World Health Organization (WHO) and the FDA. These recipes call for a mixture of 96% ethanol alcohol by volume (ABV), hydrogen peroxide diluted to 3% of its maximum concentration, and glycerol diluted to 98%. (Recipes for sanitizer with other alcohols as the base, such as isopropyl alcohol, use slightly different ratios.)

"If you're doing your due diligence, it's hard to do it incorrectly," Blaum said. 

Although the distillery initially brewed its own ethanol for sanitizer, Blaum Bros. now purchases distilled ethanol in bulk at the start of production. As hand sanitizer sales skyrocketed at the start of the pandemic, Blaum said that pure ethanol distillates were in short supply. Manufacturers who made the contaminated sanitizers flagged by the FDA may have used a high-methanol distillate from the start, given that ethanol became difficult to procure, he noted. But that's only speculation, he said.  

Buying the right sanitizer 

In its warning about tainted hand sanitizers, the FDA noted that the products were mislabeled as containing ethanol but then "tested positive for methanol contamination." Unfortunately, there may not be a sure-fire way for consumers to check their sanitizers for contamination if they do purchase mislabeled goods, Banner said. 

"I wouldn't expect the general public to know what methanol smells like," Blaum noted. While other toxins removed during distillation have distinct scents — ethyl acetate smells like nail polish remover, for example — methanol smells similar to ethanol but with a slightly more synthetic or "chemical" odor, he said. People outside the distilling business may not be able to sniff out the difference, and what's more, sketchy sanitizer manufacturers "may very well be putting a scent in the hand sanitizer" to mask any telltale odors, Blaum added. 

"I'd just follow the FDA warnings" to keep up with which sanitizers are safe, and call the poison control center with any questions about unfamiliar products, Banner said. "Be aware that sometimes 'cheap' might not always be so good," he said, adding that obscure products made by small companies "who just jumped into a market" might not be as trustworthy as established brands. In any case, it's best practice to check the FDA list before using a new product. 

Related: Here's how long the coronavirus will last on surfaces, and how to disinfect those surfaces.

In addition, the FDA warns consumers to be wary of products marketed with misleading claims, such as the ability to "provide prolonged protection" against COVID-19. No hand sanitizers are approved by the FDA before entering the market, so products labeled "FDA-approved" should also raise alarm. Products packaged to look like drinks, candy or liquor bottles, as well as those marketed as drinks or cocktails, may place children at particular risk because their outward appearance may tempt kids to drink them. 

Signs of methanol exposure 

As more sketchy sanitizers may crop up as the pandemic continues, here's what you should know about methanol exposure and its effects on the body:

"Methanol is no more toxic than ethanol," at least when first ingested, Banner noted. The trouble arises in the liver, where an enzyme called alcohol dehydrogenase metabolizes both alcohols, he said. Unlike ethanol, methanol converts into formaldehyde as it breaks down, among other metabolites; the formaldehyde then gets passed to a second enzyme that transforms the compound into formic acid. The accumulation of formic acid drives down the pH of the blood, making it dangerously acidic; that disrupts the metabolic processes required for cells to produce energy; and it leads to a buildup of waste products, such as lactate, according to a 2011 report in The Indian Journal of Ophthalmology.

This harmful combination of acidity and metabolic disruption hits nerve cells hardest, and specifically cells of the retina and optic nerves, which begin to "swell" and can be permanently damaged as a result of formic acid exposure, Banner said. But because the body takes time to metabolize methanol, it can take about four to six hours for symptoms to emerge, he said.

People who experience vision loss after methanol exposure describe their vision first going blurry and then everything looking as if they were "walking through a snowstorm," Banner said. If these individuals don't quickly receive kidney dialysis, "they will be permanently blind," he said. In addition to dialysis, people with methanol poisoning may be treated with a drug called fomepizole, which inhibits alcohol dehydrogenase and thus stops the liver's production of formic acid. More rarely, patients may be treated with doses of ethanol, because both alcohols compete for alcohol dehydrogenase and the presence of one slows the metabolism of the other.

Besides vision loss, people exposed to methanol may experience nausea, vomiting, headache, seizures or coma, according to the FDA. The earliest signs of exposure often include feeling a bit intoxicated and beginning to hyperventilate as the body reacts to increased acid in the blood, Banner added.

Originally published on Live Science.