The Chemical Composition of Rubbing Alcohol

Close up 3D rendering of ethanol molecule.
Ethanol molecule.

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One of the types of alcohol you can buy over the counter is rubbing alcohol, which is used for disinfection and may be applied to the skin to produce a cooling effect. Do you know the chemical composition of rubbing alcohol? It is a mixture of denatured alcohol, water, and agents added to make the alcohol unpalatable to drink. It may also include colorants. There are two common types of rubbing alcohol.

Isopropyl Rubbing Alcohol

Most rubbing alcohol is made from isopropyl alcohol or isopropanol in water. It is common to find isopropyl rubbing alcohol at concentrations from 68% alcohol in water up to 99% alcohol in water. The 70% rubbing alcohol is highly effective as a disinfectant. Additives make this alcohol bitter-tasting, to try to prevent people from drinking it. Isopropyl alcohol is toxic, in part because the body metabolizes it into acetone. Drinking this alcohol can cause headaches, dizziness, nausea, vomiting, central nervous system depression, organ damage, and potentially coma or death.

Ethyl Alcohol Rubbing Alcohol

The other type of rubbing alcohol consists of 97.5-100% denatured ethyl alcohol or ethanol with water. Ethyl alcohol is naturally less toxic than isopropyl alcohol. In fact, it is the alcohol that naturally occurs in wine, beer, and other alcoholic beverages. However, the alcohol is denatured or made undrinkable in rubbing alcohol, both to control its use as an intoxicant and because the alcohol has not been purified to make it safe to drink. In fact, in the US, additives make it as toxic as isopropyl alcohol.

Rubbing Alcohol in the UK

In the United Kingdom, rubbing alcohol goes by the name "surgical spirit." The formulation consists of a mixture of ethyl alcohol and isopropyl alcohol.

Rubbing Alcohol in the US

In the United States, rubbing alcohol made using ethanol must conform to Formula 23-H, which specifies it consists of 100 parts by volume of ethyl alcohol, 8 parts by volume of acetone, and 1.5 parts by volume of methyl isobutyl ketone (MSDS sheet). The remainder of the composition includes water and denaturants and may include colorants and perfume oils.

Rubbing alcohol made using isopropanol is regulated to contains at least 355 mg of sucrose octaacetate (MSDS sheet) and 1.40 mg of denatonium benzoate per 100 ml volume. Isopropyl rubbing alcohol also contains water, stabilizer and may contain colorants.

Rubbing Alcohol Toxicity

All rubbing alcohol manufactured in the US is toxic to ingest or inhale and can cause excessively dry skin if used often. In fact, if you read the product label, you'll see there is a warning against most of the common uses of rubbing alcohol.

All types of rubbing alcohol, regardless of their country of origin, are flammable. Formulations closer to 70% are less likely to catch fire than rubbing alcohol that contains a higher percentage of alcohol.