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The rapid spread of coronavirus (or COVID-19) has people clearing out shelves of hand sanitizer across the US. And if you try to buy it online, good luck -- most of it is out of stock or marked up on Amazon, Walmart.com, Bath and Body Works, Walgreens and other retailers. Target and regional grocery store Kroger now have limits on how many "anti-viral" products you can purchase at a time. And, New York Governor Andrew Cuomo announced that New York state will be producing its own hand sanitizer to address the shortages and price gouging.

The shortages and buying limits have spurred people to make their own hand sanitizer using recipes from Twitter, Reddit, Pinterest, countless blogs and even a pharmacy. But just because these recipes exist doesn't mean you should follow them.

Reasons to not make your own hand sanitizer

First, the Centers of Disease Control recommends washing your hands over using hand sanitizer, unless you don't have access to soap and water. Second, the FDA has said that it knows people are making DIY hand sanitizer at home, but that it doesn't have any "verifiable information on the methods being used to prepare such products and whether they are safe for use on human skin."

Lastly, experts caution that making homemade hand sanitizer is harder than it seems. If you don't get the concentration right, experts warn that you'll end up with something that isn't effective or is too harsh, and is a waste of ingredients.

The key is to get the right ratio of ingredients. The CDC Control recommends using a hand sanitizer that contains at least 60% alcohol, which store-bought hand sanitizers have. But trying to replicate that on your own can be tricky, Dr. Sally Bloomfield, with the London School of Hygiene and Tropical Medicine told the Guardian.

In the video below, Dr. Jason Kindrachuk, an assistant professor of Viral Pathogenesis at the University of Manitoba explains that you're better off using soap than trying to make your own hand sanitizer.

Official hand sanitizer formulas

Both the World Health Organization and the FDA have guidelines for making hand rubs (the agencies' term for hand sanitizer), but they are designed for medical professionals, not the average consumer. The WHO's official instructions call for denatured alcohol or isopropyl alcohol, glycerol (also known as glycerin), hydrogen peroxide and sterile water. You must measure the concentration of alcohol in the final product using an alcoholometer to ensure it is effective at killing germs and safe to use.

The recipe also does not recommend including any dyes, essential oils or other fragrances because they could cause an allergic response -- a lot of DIY recipes call for essential oils to mask the smell of alcohol.

On March 20, 2020, the FDA released its temporary guidelines for pharmacists and other manufacturers to make hand sanitizer. Under its recommendation, you must use pharmacy-grade ingredients, test the alcohol level in the final product, and label the finished formula. The FDA recommends the WHO's formula, and echoes that adding additional active or inactive ingredients (such as aloe vera gel or essential oils) "may impact the quality and potency of the product."

The FDA also notes that it is "aware of reports that some consumers are producing hand sanitizers for personal use; the Agency lacks information on the methods being used to prepare such products and whether they are safe for use on human skin." Unless you can follow the instructions outline by the WHO, making your own hand sanitizer just isn't smart for your own safety.

Homemade hand sanitizer recipes

Most of the countless recipes out there use a mix of 91% or 99% isopropyl alcohol (also known as rubbing alcohol) and aloe vera gel, which is necessary to add moisture to your skin because alcohol will dry it out. In these recipes, the typical ratio is two thirds rubbing alcohol to one third of a cup of aloe vera gel.

Even if you follow that recipe, you can still mess it up. Mixing it at home, you can't control how the alcohol gets diluted in the final product. If you don't use enough aloe gel, it will dry out the skin on your hands, which can cause it to crack or bleed (the same is true if you just pour rubbing alcohol on your skin).

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But if you don't use enough alcohol, the final product won't be as effective at killing germs as store-bought hand sanitizer -- rendering it basically useless according to some experts. You can also contaminate your batch with bacteria by not using clean tools to mix it together.

The final issue is that because of the popularity of these homemade hand sanitizers, the ingredients are now harder to come by. So even if you want to make it, you might not be able to find rubbing alcohol and aloe vera at your local drugstore.

You should avoid recipes that call for vodka or spirits because you need a high proof liquor to get the right concentration of alcohol by volume. That's because most liquor is mixed with water, so if you mix a 80-proof vodka (which is the standard proof) with aloe, you'll have hand sanitizer that contains less than 40% alcohol. In response to a tweet about someone using Tito's Vodka to make DIY hand sanitizer, the company responded by saying that you shouldn't use its product for that purpose.

So what should you do instead?

Wash your hands. The CDC and WHO both agree that's the best thing you can do right now to protect yourself from getting sick, either from coronavirus or anything else. Wash your hands with soap and water for 20 seconds, many times per day -- after you use the restroom, before and after you eat, before and after you prepare food and in many other scenarios.

Also avoid touching your face in general, but especially with dirty hands. Most everything you touch throughout the day is covered in germs and if you touch your mucous membranes (lips, noise, eyes) you can spread viruses and bacteria into your own body.

If you want to use other disinfecting products to clean your hands or surfaces, the Environmental Protection Agency released a full list of products that can kill the virus.

I don't advise it, but if you're determined to make your own hand sanitizer (and can actually find the ingredients to do so), avoid any recipes that don't use at least 60% alcohol. Otherwise, just wash your damn hands.

The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.