Over the past week or so, you might have read some alarming headlines about the cleanliness of jet air dryers, specifically Dyson’s Airblade. "Using a Dyson hand dryer is like setting off a viral bomb in a bathroom," read one story. "Dyson Airblades 'spread germs 1,300 times more than paper towels'," said another. Dyson, understandably, isn’t happy ("It’s just not cricket," their in-house microbiologist told The Verge). But the argument over the cleanliness of different hand-drying methods is one that’s been waged quietly for decades via studies, papers, and conferences. Getting to the bottom is a messy business.

There are a handful of major questions regarding the hygiene of jet air dryers like the Airblade: do they eject bacteria into the air during drying? Do they help remove bacteria from the hands? And are they any good at actually drying hands?

It’s just not cricket

The recent study, published in the Journal of Applied Microbiology, looked at this first question primarily. It had test subjects dip their hands in a solution of bacteria, shake them (three times — no more, no less), and then use a variety of different hand drying methods. The researchers found that jet air dryers dispersed 60 times more bacteria into the air than warm dryers, and 1,300 times more than paper towels. Sounds pretty damning.

But, as Dyson points out, the test isn’t entirely fair. It was conducted using gloved hands, making it easier to push off bacteria with air, and the bacterial solution was teeming — around 10 million infectious particles per milliliter. Speaking to The Verge, Dyson’s in-house microbiologist Toby Saville called the study "fundamentally flawed," adding: "You’d be disappointed if an undergraduate had made some of these errors." He adds that the washing method (simply shaking the hands) was also insufficient.

It sounds a little like a setup. Even more so, says Saville, when you consider that one of the paper’s authors, Keith Redway, has previously worked on a number of pro-paper-towel studies funded by the European Tissue Symposium (ETS) — an industry body dedicated to, yes, paper towels.

Redway says his study is about potential risk

Redway, though, stands by his science. Speaking to The Verge, he said that his study was all about "showing the potential for risk" with different types of hand drying. "It was a high level of contamination," he admits, "but that is possible if people don’t wash their hands properly anyway, especially with pathogenic viruses." He adds that he asked his subjects to use gloves because the experiment might have posed a danger to them otherwise, and says that although this may have influenced the test, the fact that the conditions were the same for each drying method gives a clear idea of relative risk. Unfortunately, this is not a nuance that’s conveyed in headlines like, "Dyson hand dryers spread thousands of germs."

Redway is more equivocal: "I’ve never condemned these jet air dryers or warm air dryers completely outright, but I don’t think they should be in clinical or sensitive areas where cross infection is particularly important," he says. And other studies have supported the idea (quite logically) that jet dryers disperse more particles into the air than paper towels.

As for the funding, Redway admits that while he has received money from the ETS in the past, this particular study was independently funded. He says, "The only people I’ve never been asked to do work for is the warm air dryer people and the jet air dryer people, because they don’t like what we come up with."

An infographic produced by the European Tissue Symposium based on Redway's research. (Image credit: ETS )

This caveating and counter-caveating also crops up when interrogating another measure of hygiene and hand-drying — the accumulation of bacteria on the hands during the drying process. Redway has been involved in reports showing more bacteria is left on the hands after drying with a jet air dryer than when using paper towels, but again, Dyson has objections.

A 2008 report by Redway commissioned by the ETS asked 20 test subjects to visit a public washroom. They then returned to a laboratory where their hands were tested for bacteria levels before and after washing and drying. The report says that those that dried their hands using paper towels reduced bacteria on the palms by between 32.8 and 85.2 percent, while those that used jet air dryers increased it by 9.1 percent to 82.2 percent. Again, it seems clear cut.

Saville’s criticism is that the experiment didn’t sample subjects’ hands between washing and drying — only before and after. "When you’re washing the hands, although you do wash bacteria off the surface, your skin is made up of lots of layers, and between each layers you’ve got another layers of bacteria," says Saville. "So what you do is you break up the skin, and the bacteria comes to the surface." He notes that the findings were only a report, and points to peer-reviewed studies that show no difference between the amount of bacteria left on the hands after different drying methods. (Though they don’t include jet air dryers, just warm air dryers.)

bad blood has infected the hygiene debate

The problem seems to be that the debate has been overtaken by press spin and animosity. Although while talking to The Verge, Redway defends his work by saying it was only looking at an extreme case, when he’s being quoted over at the European Tissue Symposium press site, the argument is reduced to "paper towels are great and jet air dryers are bad." Who’s at fault here? It’s difficult to say.

And Dyson isn’t blameless either. Although Saville says — and I believe him — that all he wants is a level playing field, Dyson the company makes a point of touting the dryer’s hygienic credentials, funding its own research that make paper towels seem like the unclean option. After Redway’s recent study was published, Dyson even produced a video titled "Paper’s dirty little secret," complete with a friendly but slightly menacing voiceover asking viewers: "Did you use a paper towel today? It wasn’t as hygienic as you might think." Cue the CGI images of a paper tissue covered in little snot-like bacteria. The word Dyson used to describe Redway's study was "scaremongering," but that might cut both ways.

It doesn’t help that there also seems to be bad blood between the opposing researchers. Redway describes Dyson as "quite an unpleasant company" and feels that they’ve been aggressive toward him, questioning his methods and credibility. Saville, meanwhile, says he’s had little contact with Redway (they exchanged emails once but it didn’t end well), but that he did once attend a conference incognito that the researcher was speaking at. Saville claims that Redway took the stage and ridiculed his research to the audience of pro-paper towelers. "It was pretty incendiary," he says. "He was whipping the crowd into a bit of a frenzy about it."

From an outsider’s perspective it looks like animosity might have overtaken the science, and it’s certainly true that the media hasn't helped, with sensationalist headlines raising the stakes for both sides. The thing is, if you know your research is going to be hammered into the crudest interpretation possible, then you have less incentive to be subtle yourself.

There's a germ of truth to both sides' argument

All of this seems self-defeating when you consider that Redway and Saville actually agree on what is perhaps the most fundamental and hygienically significant aspect of the Dyson Airblade: it’s very good at drying your hands. Just as good as paper towels in fact. This sounds trivial, but it couldn’t be more essential. Wet hands are magnets for bacteria. The moisture gives them a home, and if you touch dirty surfaces in a washroom with wet hands (like the door handle on your way out, for example), then bacteria is going to leap on board like it’s a pool party.

"Drying is not about removing bacteria, that’s not what it’s there for. Washing is about removing bacteria," says Saville. "The drying step is just about drying, and the reason it’s important is because if your hands are still damp, that moisture acts as a conduit for you to move bacteria […] onto your skin."

On this point, the two sides are even willing to compliment each other. "The jet air dryer, surprisingly enough, is very effective at drying — as good as a towel," says Redway. Saville adds: "The paper towel is a hygienic way to dry the hands. We’ve never stepped too far away from that." And both sides agree that it’s warm air dryers that are the bigger danger (the enemy of my enemy, you could say), as their heat and age often means they’re home to bacteria themselves, and because they work more slowly, people are more likely to get bored mid-dry and walk off with wet hands.

Focusing too much on hand drying ignores the most important step: hand washing

All this discussion of drying, though, ignores one obvious, overwhelmingly important fact: it’s washing your hands that’s key when it comes to personal hygiene, and people just don’t wash their hands enough. When you look at advice and research from agencies tasked with public health like the CDC and WHO, there’s scant mention of drying techniques because getting people to wash is tricky enough. In a UK study, 99 percent of people visiting a public bathroom said they had washed their hands after going to the toilet. Recording devices showed that only 32 percent of men and 64 percent of women actually had.

Use proper soap, is the official advice, go through these six steps, and sing "Happy Birthday" twice before you even think of finishing up. Then — and only then — can we talk about drying.