Denatonium Benzoate

by Jean-Patrick Holvoet, Master in Electro Mechanical Engineering. ©2014

Denatonium Benzoate is a bittering agent. It is considered the bitterest chemical compound with a range of uses in the manufacture of cleaners, automotive supplies as well as health and beauty items. Commercially, this compound is available as a white crystalline powder, but denatonium benzoate granules or solutions are also available.



Bitrex (r)According to Chemistry World, denatonium benzoate was an accidental formulation by researchers at T & H Smith, a Scottish pharmaceutical firm that was the precursor for Macfarlan Smith Ltd. In 1958, staff at the laboratory was working with lignocaine, a dental anesthetic, when they discovered the extreme bitterness of denatonium benzoate in powder form. Due to the extreme taste, denatonium benzoate was used as an aversive agent. It is available under the trade name Bitrex®, which is a portmanteau of the words bitter and rex for king. The first known application for Bitrex® was as an aversant for pigs that were cannibalizing their own tails or those of other pigs.


Biochemical Structure

Chemical formula: C21H29N2O . C7H5O2The chemical database PubChem assigned a chemical identification number or CID of 19518 to denatonium. It has a chemical weight of 446.58116 g/mol and a molecular formula of C28 H3 4N 2O3. Denatonium benzoate is a compound of salt with an inert anion such as benzoate or saccharide. Its structure is similar to lidocaine and is closely related to Novocain and benzocaine. It is odorless, colorless and non-reactive, making it a suitable additive that does not interfere with the primary purpose of the base compound.


How it Works

Humans can typically sense sweet, sour, salty, savory and bitter-tasting stuff. Of these flavors, bitter-tasting chemicals elicit the most reaction. Sensitivity to bitter flavors depends on genetics: The TAS2R38 gene determines a person’s ability to detect the bitterness associated with substances such as quinine, which is an ingredient in tonic water. It is also the standard for this type of bitter flavor. At a concentration of 0.008 moles per cubic meter, the human tongue can detect the presence of quinine. For denatonium benzoate, a concentration of 0.000008 moles per cubic meter is discernible to humans.



Bitterants such as denatonium benzoate are useful as aversive additives to prevent accidental ingestion of hazardous automotive compounds. In Europe and in some U.S. states, addition of denatonium benzoate is required in ethylene glycol or anti-freeze and windshield washer fluids. Common household products such as window cleaners, disinfectants, laundry detergent and insecticide include a certain amount of denatonium benzoate to discourage consumption by mouth.

It is applied on surfaces of toys as a bittering agent to prevent substantial consumption of hazardous materials. It is also applied on outdoor cables and wires to discourage rodents from chewing on parts and equipment. Denatonium benzoate is an aversive agent added to various pesticides, plant food sticks and rodenticides to suppress swallowing especially when young children come in contact with these poisonous substances.

By far, the most common use of denatonium benzoate is to denature alcohol, making it unfit for human consumption and exempt from tariffs that normally apply to alcohol.

In livestock farming, denatonium benzoate is used to prevent cannibalism in pigs and aspiration mastitis in cattle. It acts as a repellant when applied to young shoots, branches and other surfaces to discourage nibbling by animals, thereby preventing damage to property.