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The Worst-Tasting Flavor in the World Was Accidentally Discovered in a Lab

You’ve probably never tasted Bitrex, but it’s all over your home.

A pool of anti freeze, which contains the chemical bitrex. (Photo: ms.akr/CC BY 2.0)

A version of this post originally appeared on Tedium, a twice-weekly newsletter that hunts for the end of the long tail.

We love things that taste good. We hate things that taste bad.

Perhaps it’s for that reason we don’t spend a lot of time talking about terrible-tasting things. Generally, when we do, it involves encounters like Anthony Bourdain’s taste of the Icelandic delicacy hákarl, or fermented shark.

(Iceland is Not Impressed by this attempt. In a Reykjavik Grapevine piece last year, former food editor Ragnar Egilsson mocked Bourdain’s complaints. “Celebrity chef Anthony Bourdain famously called ‘hákarl’ the worst thing he had ever eaten,” Egilsson wrote. “This may have been coloured by an overall miserable visit to Iceland or by the fact that Anthony Bourdain is a huge sissy.”)

But, getting past the stunt food, there’s plenty of reason that we should talk about terrible tastes.

The biggest is this: Sometimes, hiding in that terrible taste might be something so important that it can change the world in a noticeable way. In fact, there’s a really terrible flavor that’s hiding all over your home. Why haven’t you tasted it yet? Well, let’s just say that, if the flavor does its job right, you never will.


In 2007, Aqua Dots, a toy manufacturer, had a bit of a disaster on its hands when it was discovered that at least some of the beaded toys it produced were coated with a chemical so dangerous that, when it metabolized, it turned into the “date-rape” drug GHB.

Beads are small, and they’re edible. So you can imagine what happened. The U.S. Consumer Product Safety Commission quickly recalled more than 4.2 million toys in an effort to control the problem.

But eventually, these toys came back on the market in a different form, under a different name. And when they did, they were covered with another kind of chemical—this one designed to prevent kids from eating the beads.

Aqua Dots, a toy that was recalled after the manufacturer discovered that parts were coated with a chemical that, when ingested, metabolizes to the “date rape” drug GHB.  (Photo: Anathea Utley/CC BY 2.0)

That chemical, denatonium benzoate, goes by the brand name Bitrex, and it’s been around since the 1950s. It’s currently used in substances as diverse as antifreeze, perfumes, household cleaners, and pesticides. Only recently has the chemical come to the world of toys. But it packs a hell of a punch—a single molecule of Bitrex can make a million molecules of water taste horrible.

If that level of bitterness sounds like fodder for a series of YouTube-style challenges, YouTube is already way ahead of you. Here’s a G-rated taste-test from a radio-station morning show crew that was put up to it by a nonprofit organization; here’s an R-rated test from a guy who runs a YouTube channel dedicated to eating weird things.

But as we learned in the case of Aqua Dots, this material has some important uses. One of those was discovered by the U.S. Army, which filed a patent describing “compositions and method for degrading foodstuffs.”

Other methods for turning the enemy’s food into untouchable junk were highlighted in the patent, but none were quite as memorable as Bitrex.

“This compound is several magnitudes more bitter, and the bitter taste persists in the mouth for a considerable time,” the patent stated. “Rice which is contaminated with this chemical in amounts of 0.10 pound per ton is inedible. The bitter taste was so nauseating that no one who tasted the boiled rice was able to consume as much as a teaspoonful.”

The incredibly potent flavoring of Bitrex didn’t have a ton of uses at first, but eventually, it proved handy for a problem that arose in the early ’80s, when reports of children being hospitalized for accidentally ingesting household chemicals became commonplace.

The logic is simple. If you make dangerous chemicals taste bad, kids won’t eat or drink them.

As New Scientist explained in a 1985 article:

The sensible answer, then, is to make these household chemicals taste so repellant to a child that its immediate reaction if it puts some in its mouth is to spit it out. What is required is a compound so vile in taste that it cannot be tolerated. There are, in fact, several such substances, both natural and man-made, but one that stands out above all others is denatonium benzoate, or Bitrex, as it is commonly known. This white, non-toxic powder, which is soluble in both aqueous and organic solvents, is listed in the Guinness Book of Records as the bitterest substance known. Adding just one teaspoon of powder to a tankerful of water would make the water undrinkable.

Problem was, it wasn’t a given that household cleaner manufacturers would use this substance, particularly in the U.S.

That’s where the hard work of an Albany, Oregon, woman named Lynn Tylczak came into play. Tylczak heard about Bitrex getting used in cleaners made in Europe, but found out that the issue was getting ignored in the U.S.

In the 1980s, well before the days of email, she started a letter-writing campaign—first with chemical manufacturers, then with politicians, neither of which she had much luck with. She had a much better track record, however, when she and 20 of her neighbors started reaching out to the media and various consumer groups about the problem.

Bitrex is added to household cleaners so that they taste bad. (Photo: Mike Mozart/CC BY 2.0)

“I wrote to about 20 of the big newspapers, then I wrote to consumer groups, magazines, health magazines, insurance magazines, the people I thought would pick it up,” Tylczak told the Los Angeles Times in 1989.

The media notice worked; soon, the politicians (including New York Sen. Chuck Schumer, then a member of the House) were knocking on her door pledging support. Noted consumer advocates, like Ralph Nader, were singing Tylczak’s praises, and the National Safety Council quickly called on manufacturers to add Bitrex to their products.

As it turned out, at least one company, Procter & Gamble, already had. After doing market research in the early ’80s, the company added the chemical to two varieties of laundry detergent after it was found that children were more susceptible to drinking those kinds of detergents over others. But its comments highlighted the fact that resistance lingered.

”We don’t advertise the use of Bitrex because we don’t want to communicate the notion that our products are not safe if they don’t have Bitrex,” company spokeswoman Jennifer G. Bailey told The New York Times. ”All of our products contain an emetic that would induce vomiting.”

Procter & Gamble was nothing compared to the antifreeze industry, which apparently got a PR firm to spy on her operation, according to a Covert Action Quarterlyreport.

Bottles of anti-freeze. (Photo: Anthony Easton/CC BY 2.0)

She recalled in comments to The Giraffe Project: “One major antifreeze manufacturer saw the Poison-Proof Project on CNN and decided to use bittering agents. His comment was, ‘It would cost us more to fight this than to do it.’ Doesn’t anybody just plain want to make a safe product?”

Within a year and a half, the success of Tylczak’s grassroots efforts were bearing fruit—she quickly became a fixture on television talk shows, her efforts had gotten notice in Congress, and the industry started changing its ways. And in 1995, a law requiring antifreeze to contain the chemical was passed in Oregon.

These days, Bitrex is commonly used in all sorts of products you shouldn’t drink. So if you accidentally have a toxic chemical in front of you and you feel like taking a swig, you can thank Lynn Tylczak for ensuring that you spit it out almost immediately. (Not that you should even try to drink a toxic chemical. That’s stupid.)


Bitrex’s discovery may have a bit of accident, but the world of chemical production doesn’t have a monopoly on terrible-tasting things. And, as any foodie knows, “bitter” doesn’t necessarily mean “terrible.” Author and chef Jennifer McLagan, for example, wrote an entire cookbook playing up the appeal of bitter foods. In an interview with Publishers Weekly, she emphasized that the decline of human taste buds actually does adults a favor.

“As we age, we don’t have as many taste buds, and we can get used to bitter flavors,” she explained. “As we experience more bitter flavors, we are more likely to crave and appreciate the digestive powers of bitter, which can, for example, balance fatty foods.”

In other words, bitter is an acquired taste.

Consider, as well, durian, an incredibly smelly fruit that some people either love or hate.

One food writer, Richard Sterling, describes the smell as “turpentine and onions, garnished with a gym sock. It can be smelled from yards away.”

Smithsonian magazine, in a piece on the bizarre fruit, says that scientists have analyzed that smell, in an attempt to nail down why it’s so pungent, and have found a situation unlike that with Bitrex. It’s not a single chemical compound—but numerous ones, each evoking different kinds of smells. At least 50 different ones, many of them things you wouldn’t want to smell individually, let alone mashed into one super-smell.

If you truly wanted to mess with someone, obviously, you would put Bitrex on a durian. Sounds like an endurance test I’d watch on YouTube.

A version of this post originally appeared on Tedium, a twice-weekly newsletter that hunts for the end of the long tail.