The guidelines are everywhere: You should be washing your hands regularly to help stop the spread of infectious diseases, including COVID-19. But does the temperature of the water matter? What's the right way to dry your hands? Why is washing your hands better than using hand sanitizer?

We talked to hand-washing researchers and specialists to learn more about the most effective steps.

Prep

If possible, you should remove jewelry like rings, bracelets and watches first so you can scrub your hands without anything getting in the way. But "that's not always realistic," says Tania Busch Isaksen, a lecturer at the University of Washington's department of environmental and occupational health sciences. If you're leaving the jewelry on, just try your best to wash around and under it as much as the jewelry allows.

Wet Your Hands

Start by wetting your hands with cold, lukewarm or warm water. These temperatures are all fine in facilitating the removal of pathogens from your hands. "The idea is just that you don't want to use really hot water," says Erin Sorrell, an assistant professor of microbiology and immunology at Georgetown. If your hands dry out from using hot water, that could lead to cracks in your skin that expose you to infections, she says.

You wet your hands before adding soap so that the water can help the soap dissolve and do its job of removing dirt and germs, Sorrell adds.

You won't need running water again till you rinse, so you can turn off the tap (which will save water).

Lather Up

Soap is critical to killing germs on your hands. SARS-COV-2, the virus that causes COVID-19, is wrapped in a membrane that can be broken up by the lather from soap, says Dr. Mark Gendreau, the chief medical officer at Beverly Hospital in Massachusetts. That renders the virus particles unable to infect you.

You don't have to be picky about which kind of soap you use. Antibacterial or regular soap — in liquid or bar form — will work. But "you want to use enough soap that you're going to get a good lather," Gendreau adds.

It's most important to maintain the lather as you're scrubbing, Busch Isaksen says. You can always add a little more soap if needed to make sure you see a healthy crop of bubbles on your hands throughout the 20 seconds. This is a good sign that you have enough lather to break up virus particles.

Timing

The common guideline is 20 seconds, but you're actually going to need a bit more time than that. "The 20 seconds start when you have the soap in your hands, in the lathering process," Sorrell says.

Scrub

Microbes, including viruses, can take up residence all over your hands, so you want to make sure you're hitting all the areas. Fingertips, thumbs and spots between your fingers are commonly missed, Sorrell says.

One step in the World Health Organization's guide suggests rubbing your fingers against the opposite palm — a move designed to clean your fingertips and get some soap under the tips of your nails, Gendreau adds.

"Depending on the length of your nails, it can be more difficult to really get under there," Sorrell says. She recommends rubbing the edges of your nails against your palms.

Rinse

Rinse the soap away — along with the pathogens.

Turn off the water

It's a snap when using touchless faucets. But not every restroom or home bathroom is so equipped. WHO guidelines suggest using a paper towel to turn off the faucet lest you pick up pathogens from the faucet itself. But there isn't clear research showing this actually keeps you healthier in the long run, according to the CDC.

Nonetheless, Gendreau, Sorrell and Busch Isaksen all advise that you don't directly touch the faucet. Faucets are "worry spots in terms of areas that could be contaminated in restrooms," Gendreau says.

You shouldn't touch the faucet handle with your clean hands, Busch Isaksen adds. "You just turned that on when they were dirty, so now you're recontaminating your hand."

Dry

Wet hands can pick up germs more easily than dry hands, the CDC says. Without drying, "you're more prone to contaminating yourself" when your newly washed hands encounter germs from other sources, Gendreau adds.

But it's not totally clear which way of drying your hands is best — if you should use paper towels, a cloth towel or air blowers, Busch Isaksen says. "This is a point of controversy."

Paper towels are a good option, according to Busch Isaksen, Gendreau and Sorrel. There's not enough evidence to say whether air blowers are any better or worse, according to Dr. Vincent Hill, chief of the CDC's Waterborne Disease Prevention Branch.

Sorrell recommends "only touching the towels that you will be using yourself." Or if you're at home, a cloth towel works as long as you wash those towels in a washing machine with detergent every couple of days.

Sharing a towel with other people in your household isn't ideal, Busch Isaksen says. And if someone you live with is sick, that individual definitely should get a personal-use towel.

Door dilemma

Once the faucet is shut off and your hands are dry, you might encounter another potential source of infection — the door handle of the bathroom. It's a good precaution to use another part of your body, or a paper towel, to open the door when you're leaving the bathroom, Sorrell says. More germs could lurk on the door handle.

What about hand sanitizer?

If you don't have access to soap and running water, hand sanitizer is a good backup, Busch Isaksen says. Just make sure it's at least 60% alcohol, since sanitizers with less alcohol than that might not kill as many germs. "With hand sanitizer, you're applying that. Dirt and grime can remain on your hand and sometimes can hide the bacteria and virus particles," she warns. Any debris on your hands might have these germs within it, and hand sanitizer won't necessarily get to them. "Hand washing is far superior."

Editor's note: This story has been revised to include more complete information on hand-washing procedures.

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