At the peak of the pandemic’s rabid stockpiling, store shelves had been picked clean of recognizable brands of hand sanitizer such as Purell, Germ-X, and even drugstore formulations. An extensive online search finally turned up an industrial-size, 1-gallon plastic bottle containing 70% ethyl alcohol “specially denatured with a mild lavender scent.”

Ordering it required a wait of over two months, but its eventual arrival produced a sense of relief.

It didn’t last long.

Opening the bottle revealed what could be described only as the funky marriage of rotting corncobs paired with pungent notes of barnyard odors, a repulsive nose-wrinkling scent that lingered and wafted far and wide with every use.

You, too, might have noticed that the assorted new brands of hand sanitizers smell ... different. Various no-name brands have sprung forth to meet market demand, and many share a common trait: an unpleasant scent. Some exhibit an organic rot, while others emit an acrid alcoholic sharpness prone to stinging the nose. None have been as benignly pleasant to use as brands purchased before the pandemic shortage.

To find out why these new hand sanitizers stink, we turned to the experts: Bryan Zlotnik, chief operating officer of fragrance manufacturer Alpha Aromatics; Pamela Dalton, co-chair of the Monell Chemical Senses Center; and Li Wong, a vintage aromatherapist, environmental scientist and biologist and natural perfumer.

Waterless hand sanitizers for the general public caught on in 1988 with the birth of Purell Hand Sanitizer, an easy-to-use concoction of 70% ethyl alcohol mixed with propylene glycol (a moisturizing compound) that masked most of the disagreeable scents associated with using alcohol in gel form by including a mild proprietary citrus scent.

And here’s where the mystery begins: That’s the same formula used by today’s knockoff brands. So why do they stink?

“That off-putting smell is the natural byproduct of ethanol being made from corn, sugar cane, beets and other organic sources,” explained Zlotnik. “[Ethyl alcohol] production is highly regulated. It stinks because these new brands — many made by distillers who’ve pivoted from producing drinking alcohol to meet public demand for hand sanitizer — are making and using denatured ethanol. This ethanol costs significantly less than ethanol filtered using activated carbon filtration, which would typically remove almost all contaminants and the malodor with it.”

Those organic contaminants aren’t the only reason unfiltered and denatured ethanol smells foul. According to Zlotnik, denatured ethanol is intentionally tainted with an unpalatable cocktail of chemicals (denaturants) such as methanol, acetone, methyl ethyl ketone and denatonium to make it undrinkable. In other words: The base material is intentionally stinky.

Sniff test

So should we be making our own hand sanitizer at home instead, as numerous social media how-to posts propose as an answer to the world’s sanitizing woes? Li doesn’t think so.

“I do not recommend that the average person make their own hand sanitizer. Nearly every single recipe I have seen online or on the news has been improperly formulated,” she said. “If you are in a pinch, I suggest either using ethyl alcohol or isopropyl alcohol in a spray bottle. (The alcohol concentration needs to be at least 60% to be effective.)

What if you’re already stuck with a gallon of hand sanitizer polluted by malodor? Is there anything you can add to mask the smell?

As of now, there are no masking agents available to the public (although Zlotnik said his company is close to having one), and Li advised that adding untested elements to sanitizers could compromise the formula. For the time being, your safest bet is to sniff before you buy.

All that said, smelly hand sanitizer might have a silver lining.

“The malodor is a potent behavioral message to keep our hands away from our face, which is something we should be doing anyway,” said Dalton. “While I normally do not want my hands to smell like a farm, it certainly did keep me from putting my hands anywhere near my face — and that could be a good thing!”

Correction: Previous versions of this article misstated the title of Bryan Zlotnik.