Denatonium(Denatonium Benzoate), is the most bitter chemical compound known, with bitterness thresholds of 0.05 ppm for the benzoate and 0.01 ppm for the saccharide, dilutions of as little as 10 ppm are unbearably bitter to most humans. It’s used as aversive agents (bitterants) to prevent inappropriate ingestion, i.e. Denatonium is used in denatured alcohol,[4]antifreeze, nail biting preventions, respirator mask fit-testing, animal repellents, liquid soaps, and shampoos.