Would you say you’re more of a hand sanitizer person, or do you typically go the soap and water route? Believe it or not, this is a real debate, with heated defenders on either side. And with flu season in full swing, it’s as good a time as any to settle things once and for all — by looking to science to provide us with the best and most evidence-based germ-busting answers, of course.

The importance of clean hands

According to the U.S. Department of Health & Human Services (HHS), the flu is caused by viruses (aka very small germs) and, in many cases, viruses can spread easily from one person to another, which is what makes the flu contagious.

The HHS provides examples like viruses living on a friend’s phone or doorknob and being transmitted to your skin when you touch these surfaces. If the virus then transfers to your hands and you touch your nose, mouth, or eyes (which happens more often than you think), you could catch the flu. That’s why disinfecting is so important.

But again, should you be meandering to the sink or whipping out your mini Purell?

Hop on that soapbox

“Washing your hands with soap and water for at least 20 seconds is the most effective way of sanitizing your hands,” Dr. Nikola Djordjevic, MD and Co-Founder of MedAlertHelp.org tells Considerable.

According to Djordjevic, washing your hands (properly! — more on that in a bit) allows you to fully cleanse all the crevices and folds in the skin from organic matter and bacteria.

The Centers for Disease Control and Prevention (CDC) confirms the notion that hand-washing trumps sanitizing for a multitude of reasons, including sanitizer’s decreased effectiveness when hands are visibly dirty/greasy. It also doesn’t work to eliminate all types of germs and harmful chemicals (specifically, hand-washing removes the germs Cryptosporidiumnorovirus, and Clostridium difficile, while hand sanitizer does not).

Further, the CDC states that although alcohol-based hand sanitizers can inactivate many types of microbes very effectively when used correctly, people may not use a large enough volume of the sanitizers or may wipe it off before it has dried.

Still, sanitizer has its benefits

“With that being said, hand sanitizer can be very effective as well,” says Djordjevic. “Especially when you don’t have the convenience of accessing a sink.”

But in order for hand sanitizer to be the most effective, notes Djordjevic, it needs to have an alcohol content of at least 60%. “In this case, it’s almost as effective as soap and water (provided you rub your hands for at least 30 seconds),” states the doctor.

Many brands of hand sanitizer are too low in alcohol content but are still marketed as good products for personal hygiene. Again, this is supported by the CDC: The organization cites numerous studies in which sanitizers with an alcohol concentration between 60 to 95% are found to kill germs more efficiently than lower concentration brands or non-alcohol-based hand sanitizers.

When should I use?

If you’re able to opt for soap and water, the CDC recommends washing your hands before, during, and after preparing food, around other sick individuals, before and after treating a cut or wound, after using the bathroom or changing diapers, after blowing your nose, coughing or sneezing, after being around animals, after touching garbage, or if your hands are visibly dirty or greasy.

Though that may seem like an intimidating list, it’s basically just saying that you should wash your hands any time you’re exposed to germs or bacteria.

The only time you should opt for hand sanitizer is when you don’t have access to a sink with running water.

The only exception, states the organization, is if you’re visiting someone in a hospital or nursing home — then, it would actually be more effective to use hand sanitizer (unless the person is sick with Clostridium difficile).

How should I use?

When washing your hands, live and breath by the “wet, lather, scrub, rinse, dry” mantra. And, if in doubt about how long you should be washing, err on the side of safety by humming (or singing — we won’t judge) the Happy Birthday song twice.

If you’re in a pinch and need to use hand sanitizer, just make sure you’re covering the total surface area of your hands and rubbing them until they’re completely dry.

“Either way, soap/water is still the best way to prevent a cold or a flu, provided you have access to a sink with running water,” Djordjevic concludes.

Sorry, sanitizer fanatics.