Solver World With the current COVID-19 crisis, most retail and online stores have been unable to keep hand sanitizer in stock. This has created a crisis for people that need to clean their hands and are unable to access soap and water. The CDC recommends hand washing for 20 seconds frequently to avoid contamination 1. If this is not possible, they recommend using a hand sanitizer with at least 60% alcohol.
Because of the shortage of commercial hand sanitizer, recipes have been circulating on social media for a homemade or DIY (Do It Yourself) version. While there is rarely any scientific standing behind these recipes, there is also a long standing recipe published by the World Health Organization (WHO). Putting aside any possible problems people may have following these recipes precisely enough to make an effective hand sanitizer, I want to address one deadly consequence that could occur from faulty or improper manufacturing practices.
It is possible that someone attempting to make their own hand sanitizer in this crisis situation makes one simple, deadly, mistake. They use an alcohol containing a small amount of methanol.
First, some background. The alcohol that is used in what are commonly called alcoholic drinks is ethyl alcohol (sometimes called ethanol). It is taxed by the Federal government (in the US) at a rate of $13.50 per proof gallon 2. A proof gallon is 1 gallon at 100 proof, or 1.25 gallons of 80 proof, and so on.
Two other kinds of alcohol are isopropyl alcohol and methanol (methyl alcohol). Isopropyl alcohol is what people commonly buy as rubbing alcohol, with percentages of alcohol ranging from 70% to 95%. Methanol is sold for use as fuel in camping stoves (alcohol stoves) and as a thinner for various paints, such as shellac.
The problem with methanol is that it is deadly toxic to humans. It only takes 10 mL (about 1/3 of an ounce) to cause blindness in an adult, or 30mL to cause death 3. It is the impurity in moonshine (or any improperly distilled spirit) that can make it deadly.
The other property of methanol of note is that it is absorbed through the skin. In fact, it is absorbed at the rate of 2mg/cm2/hr. That may not seem like much, except that the hand surface area is about 2% of your total body surface area, which amounts to roughly 40 cm2 for two hands. It is left as an exercise for the reader to determine just how long you can rub methanol on your hands before suffering disastrous consequences, including neural toxicity, blindness, and death. Hint: not very long and not something anyone should try.
