Earwax and Dandelion sap: what does the world’s most bitter substance taste like?

Bitrex, the world’s most bitter substance, would put a standard pint of ‘bitter’ IPA to shame. Elliot Gardner finds out more about its uses and history.


For many a pint of bitter ale, despite its name, isn’t actually anywhere near bitter enough for their taste. Chemical and technology company Johnson Matthey produce a chemical substance in their Scotland factory that is so bitter that it would give those beer drinkers quite a shock – Bitrex.

The product is the most bitter substance known to man, so strong that quantities as low as ten parts per million are unbearable to human taste buds. You’d even be able to taste a thimble-full of Bitrex in a swimming pool of water. This is certainly not a substance that you would like to drink; in fact, one of its first uses was actually the denaturing of alcohol, ensuring that industrial varieties didn’t enter into the food market.

Bitrex was actually discovered by accident, as part of Johnson Matthey’s routine work with lidocaine, a chemical used in dental work. Lidocaine has a very bitter taste, but chemists came across a derivative so bitter that they theorised it could be put to an entirely different purpose.

Promoting human aversion: record-breaking bitterness

“We as humans have a natural aversion to bitter tastes,” explains Bitrex business manager at Johnson Matthey Gina Mercier, “we evolved as hunter-gatherers. If berries were bitter you knew not to consume them as they could be poisonous - that's really the way Bitrex works as well.”

Because of its extreme taste, the inclusion of Bitrex in product formulation means people will naturally avoid consumption. While this rules out the substance for use in food products, it does prove incredibly useful in preventing children and those suffering from dementia from accidentally ingesting harmful goods. In fact, Bitrex is now found in more than 5,000 different products, from detergents, to rodenticide, to children’s finger paints.

As well as being found in conventional goods, over the years Bitrex has had some bizarre uses. “Farmers putting it on pig's tails to stop them from self-cannibalising was one of the very first applications,” says Mercier, “and I think today the strangest is it being put into elephant’s beds in zoos to stop them eating their bedding.” In France, it’s even legally mandatory to include Bitrex in slug bait in order to prevent passing dogs and cattle from consuming it.

Due to the strong reactions people have at the taste, The ‘Bitrex taste test’ has become popular online. But as well making people squirm on YouTube videos, Mercier explains how the test actually has a much more important and educational purpose. “The taste test is used as a tool for parents and carers, as a reminder to keep products out of the way of children. As consumers, we can get a bit tired of hearing 'don't do' messages. The Bitrex taste test is a way of talking to people in an accessible manner.” The Bitrex team coordinates with the Child Accident Prevention Trust to educate parents, especially during UK Child Safety Week, of the dangers of leaving toxic products in the reach of children.

But what does it actually taste of? The Guinness World Records lists Bitrex as the bitterest substance ever discovered, and according to Mercia, people who taste it find it difficult to draw a comparison. “When people have had to associate the taste there are two things that stand out. The first is earwax, which is frankly revolting, and the other is the sap of a dandelion, which many have eaten accidentally as a child.”