Everyone agrees, including the Centers for Disease Control and Prevention (CDC), that if you want to avoid the transmission of disease — including COVID-19, caused by the novel coronavirus — the best way to do that is to wash your hands thoroughly with soap and water for at least 20 seconds and avoid touching your face. But if you’re traveling or otherwise don’t have access to soap and water, the next best thing is hand sanitizer.

Can’t find one? You’re not alone. With increasing public awareness about the novel coronavirus outbreak, hand sanitizer is becoming difficult — if not impossible — to find. (A quick search on Amazon found most pocket-sized dispensers and wipes are listed as “currently unavailable.”)

However, if you really want some to carry around and can’t find any at your local Walgreens or CVS, you can make your own — and it really isn’t that hard. A wide range of sites (most of which are about saving money or reducing dependence on commercial products) have published explanations on how to mix up your own hand-sanitizing formula.

Recipes differ slightly (for example, some recommend adding a scented oil while others keep that step optional), but there is general agreement that if you want to create your own hand sanitizer, you need to be aware of a few things:

• To be effective, hand sanitizer needs to have a strength of at least 60 percent alcohol. Since you’re going to have to mix your sanitizer with aloe vera gel in order to stabilize it and protect your hands, most recipes suggest that the mixture contain at least two-thirds 99 percent isopropyl alcohol and one-third gel. A 91 percent alcohol would work as well. (You can probably ignore the occasional suggestion to use vodka instead of isopropyl alcohol since many vodkas are only 40 percent alcohol. And anyway, why waste good liquor?)
• On the other hand, the ethanol (also known as ethyl alcohol) in distilled beverages, such as vodka, is also effective. In fact, it’s actually considered more effective against some types of infectious diseases than isopropyl alcohol. But in order to get the proper strength, you’d have to find alcohol that is 180 proof or higher.
• Sanitizer is only effective if you cover your hands thoroughly and then let them dry. Squirting a few drops into your palms and then wiping your hands isn’t going to help at all.
• If your hands are heavily soiled or greasy, then, according to the CDC, hand sanitizer isn’t going to do much

Given a choice, though, the best thing you can do is wash your hands and keep them away from your face.

Oh, and about your phone? There hasn’t been a lot of information (or concern) out there about spreading the novel coronavirus via your mobile devices, so don’t sweat it. However, since your phone is, according to the CDC, a “high-touch surface,” if you have any concerns, you can use alcohol wipes to clean it off.

Update March 4th, 10:15AM ET: This article has been updated to add information about using ethyl alcohol (ethanol) as well as isopropyl alcohol when making hand sanitizer and that 91 percent isopropyl alcohol can be used as well.