Tag Archives: germs

Sanitizing homes gets rids of bacteria but makes room for fungi

Researchers have found that using cleaning products is effective at eradicating bacteria. However, the downside is cleansing the home of bacteria makes room for other microbes, such as fungi.

The findings were reported by researchers at the University of Oklahoma, who compared the microbial diversity in rural and urban homes from Peru and Brazil. They took samples from four locations in increasingly urban settings: from huts in the rainforest to city apartments in Manaus, the capital and largest city of the Brazilian state of Amazonas.

Samples were taken off the walls, floors, and countertops of the homes, as well as skin swabs from pets and people.

As the researchers converged towards more urban homes, bacterial diversity decreased, including so-called ‘good’ bacteria, some of which live in our gut. Meanwhile, fungal diversity actually increased in urban homes. Among them are fungi from the Malassezia genus, which contains strains that are known to cause infections.

This is probably due to the cleaning solutions that specifically target bacteria. Fungi, which have thick cell walls, are much harder to kill than your run-off-the-mill bacteria. And since urban homes are such good insulators, trapping CO2 and blocking sunlight, they’re also hospitable environments for the fungi. These differences in bacteria and fungi were also found on the skin of humans, not just in their homes.

“Maybe they’re scrubbing away all the bacteria and now you have this big open surface for fungi to grow on; maybe [the fungi] are also becoming more resistant to the cleaning agents that we use,” Laura-Isobel McCall, a biochemist at the University of Oklahoma, told NPR.

Besides bacteria, fungi, and some parasites, the researchers also tested the chemicals found inside the apartments. They found many more synthetic chemicals inside urban homes than in rural ones, sourced from items such as building materials, medications, and personal care products. In other words, urban environments are extremely artificial compared to rural ones — and these findings likely aren’t limited to Peru and Brazil.

If anything, this study shows that our efforts to sanitize our homes may never be satisfying. When you throw out one kind of germs, you’re just making room for other germs to break in.

The findings appeared in the journal Nature Microbiology.

Tracy Caldwell Dyson in ISS Cupola.

The International Space Station is teeming with bacteria and fungi

Where humanity goes, microorganisms boldly follow.

Tracy Caldwell Dyson in ISS Cupola.

Self-portrait of Tracy Caldwell Dyson in the Cupola module of the International Space Station observing the Earth below during Expedition 24.
Image credits NASA / Tracy Caldwell Dyson via Wikimedia.

New research is pinpointing exactly who makes up the microflora on the International Space Station. The study — the first comprehensive catalogue of the bacteria and fungi on the inside surfaces of the ISS — can be used to develop safety measures for NASA for long-term space travel or living in space.

Space bugs

“Whether these opportunistic bacteria could cause disease in astronauts on the ISS is unknown,” says Dr Checinska Sielaff, first author of the study. “This would depend on a number of factors, including the health status of each individual and how these organisms function while in the space environment. Regardless, the detection of possible disease-causing organisms highlights the importance of further studies to examine how these ISS microbes function in space.”

Microflora can have a range of impacts on human health, so it pays to know exactly what you’re up against — especially in space. Astronauts show an altered immune response during missions, which is compounded by the difficulty of giving them proper medical care. The team hopes that their catalog can give future space mission planners a better idea of which bugs accumulate in the unique environments associated with spaceflight, how long each strain survives, and their possible impact on the crew and the ship itself.

Despite the exotic setting, the team used pretty run-of-the-mill culture techniques to sample the microflora of eight different locations inside the ISS. These included the viewing window, toilet, exercise platform, dining table, and sleeping quarters. The samples were taken during three flights across 14 months’ time, so the team could get an idea of how the tiny organisms fared over time. Genetic sequencing methods were used to identify the strains in these samples.

All in all, the team reports finding mostly human-associated microbes on the ISS. The most prominent included Staphylococcus (26% of total isolates), Pantoea (23%), and Bacillus (11%). The analysis also revealed the presence of bugs considered to be opportunistic pathogens here on Earth — such as Staphylococcus aureus (10% of total isolates identified), which is commonly found on the skin and in the nasal passages, and Enterobacter, which is associated with the human gastrointestinal tract. Opportunistic pathogens are regulars in gyms, offices, and hospitals, the team explains, suggesting that the ISS’s microbiome is also shaped by human occupation, as is similar in microbiome to other built environments.

But it’s not all about the crew.

“Some of the microorganisms we identified on the ISS have also been implicated in microbial induced corrosion on Earth. However, the role they play in corrosion aboard the ISS remains to be determined,” says Dr Urbaniak, joint first author of the study.

“In addition to understanding the possible impact of microbial and fungal organisms on astronaut health, understanding their potential impact on spacecraft will be important to maintain structural stability of the crew vehicle during long term space missions when routine indoor maintenance cannot be as easily performed.”

Fungal communities were quite stable over the study’s period, but microbial communities changed over time (but not across locations). Samples taken during the second flight mission had higher microbial diversity than samples collected during the first and third missions. The authors suggest that these temporal differences may come down to which astronauts are aboard the ISS at any given time. Dr Venkateswaran hopes this data can help NASA improve on-board safety measures, and that they will pave the way to safe, deep space human habitation.

“The results can also have significant impact on our understanding of other confined built environments on the Earth such as clean rooms used in the pharmaceutical and medical industries,” he adds.

The paper “Characterization of the total and viable bacterial and fungal communities associated with the International Space Station surfaces” has been published in the journal Microbiome.

Credit: Pixabay.

Sunlight kills indoor germs almost as well as UV rays

We know that sunlight is important to our health, regulating sleep and mood. A new study, however, suggests sunlight also keeps us healthy by destroying bacteria that lurk indoors. The sanitizing effects are impressively close to those of ultraviolet light.

Credit: Pixabay.

Credit: Pixabay.

For their experiment, researchers at the University of Oregon collected dust from homes in Portland and placed it in dollhouse-sized rooms. The dust inside the tiny rooms — and the microscopic creatures that lived within — stayed there for 90 days under three conditions: exposed to daylight through regular glass; UV light alone; and total darkness.

When the team counted and inspected the bacterial samples, they were surprised by what they found. Lit rooms seem to harbor only half as many viable bacteria when compared to dark rooms, and nearly as few as those in the UV room. Researchers found 12% of bacteria in dark rooms were viable, compared to 6.8% in daylit rooms and 6.1% in rooms with UV light only, according to the findings published in the journal Microbiome. 

Ultraviolet (UV) light is a form of light that is invisible to the human eye, occupying the portion of the electromagnetic spectrum between X-rays and visible light. One of the biological characteristics of UV light is that it is germicidal – meaning it is capable of inactivating microorganisms, such as bacteria, viruses, and protozoa.

Today, UV light-based devices are used for drinking and wastewater treatment, air disinfection, the treatment of fruit and vegetable juices, as well as a myriad of home devices for disinfecting everything from toothbrushes to tablet computers. But soon enough, smart blinds that allow some of the solar energy to pass through and kill germs for us may become commonplace in our homes.

The study’s results were quite unexpected, however, because glass is known to block out most UV rays. The findings suggest that having a well-lit room can help protect residents from all sorts of infections. For instance, some of the bacterial species that didn’t survive the daylight rooms are known to cause respiratory disease.

“Our experimental and simulation-based results indicate that dust contains living bacterial taxa that can be inactivated following changes in local abiotic conditions and suggest that the bactericidal potential of ordinary window-filtered sunlight may be similar to ultraviolet wavelengths across dosages that are relevant to real buildings,” the authors concluded.

Next, the team plans to gain a more nuanced look at the relationship between daylight exposure and bacterial inactivation. This way, architects can then design the perfect windows that are just big enough to let enough light in to kill dangerous germs. But, perhaps the most important takeaway is that you should pull the blinds and let some of that light shine your room for longer during the day.

Credit: Wikipedia.

What is antibiotic resistance: everything you need to know

Antibiotics are medicines that combat infections caused by bacteria. However, due to misuse and overuse of antibiotics, many bacterial strains are developing antibiotic resistance.

antibiotic resistance art

Credit: Wikipedia.

Before Alexander Fleming discovered penicillin in 1928, there was no effective treatment for infections such as pneumonia, gonorrhea or rheumatic fever. Fleming’s discovery kicked off a golden age of antimicrobial research with many pharmaceutical companies developing new drugs that would save countless lives. Some doctors in the 1940s would famously prophesize that antibiotics would finally eradicate the infectious diseases that had plagued humankind throughout history. Almost a hundred years later since Fleming made his milestone discovery not only are bacterial infections still common, the misuse and overuse of antibiotics are threatening to undo all of this medical progress as bacterial strains become resistant. 

Antibiotic resistance: a modern problem that can be traced to ancient times.

Contrary to common belief, human exposure to antibiotics isn’t confined to the modern era. Traces of tetracycline, a broad-spectrum antibiotic, have been found in the skeleton remains from ancient Sudanese Nubia dating from 350-550 CE. Likewise, tetracycline has been found in remains dating from the late Roman period in the Dakhleh Oasis, Egypt. These people must have included tetracycline in their diet — and it was to their good fortune as the rate of infectious diseases documented in Sudanese Nubian populations was low. For thousands of years, Chinese herbalists have been using a variety of plants which contain antimicrobial active components for ancient traditional remedies.

Naturally, the selective pressure imposed by these ancient antimicrobial activities has led to the accumulation of antibiotic resistance genes. But that’s nothing like the scale and intensity of antibiotic resistance we’re seeing today.

What is antibiotic resistance

Antibiotic resistance occurs when an antibiotic is no longer effective at controlling or killing bacterial growth. Bacteria which are ‘resistant’ can multiply in the presence of various therapeutic levels of an antibiotic. Sometimes, increasing the dose of an antibiotic can help tackle a more severe infection but in some instances — and these are becoming more and more frequent — no dose seems to control the bacterial growth. Each year, 25,000 patients from the EU and 63,000 patients from the USA die because of hospital-acquired bacterial infections which are resistant to multidrug-action. The ECDC/EMA Joint Working Group estimated in 2009 that the cost due to multidrug-resistant bacterial infections amounts to EUR 1.5 million in the EU alone. According to a 2013 CDC report titled “Antibiotic Resistance Threats in the United States, antibiotic resistance is responsible for $20 billion in direct health-care costs in the United States.

Antimicrobial resistance threatens to undermine all the immense clinical and public health progress we’ve come to achieve so far. This is a very complex problem that requires concentrated and coordinated efforts of microbiologists, ecologists, health care specialists, educationalists, policy makers, legislative bodies, agricultural and pharmaceutical industry workers, and the public to deal with.

The main challenges in dealing with antibiotic resistance are, on one hand, genetically acquired immunity and, on the other hand, fewer and fewer novel drugs. Since the 1970s, the rate at which new antibiotic classes have been discovered has continued to drop. No novel drug classes have been developed in the last 20 years. Researchers nowadays agree that, at this current rate, humanity is destined to lose the arms race as sooner or later bacteria will acquire resistance to modified versions of currently available antibiotic classes.

How bacteria develop resistance to antibiotics

Schematic by MeMed.

Schematic by MeMed.

Every time a person takes antibiotics, sensitive bacteria are killed, but resistant germs may be left to grow and multiply. In time, these leftover populations can become so strong that antibiotics no longer are effective.

There are several mechanisms bacteria employ to become resistant. Some gain the ability to neutralize the drug before it gets the chance to attack the bacteria. Other bacteria can rapidly pump the antibiotic out or can even change the attack site so the function of the bacteria isn’t affected.

Whenever bacteria survives an antibiotic onslaught, it can acquire resistant through mutation of the genetic material or by ‘borrowing’ pieces of DNA that code for the resistance to antibiotics from other bacteria, like those from livestock. Moreover, the DNA that codes the resistance is grouped in an easily transferable package which enables the germs to become resistant to many antimicrobial agents.

The types of bacterial resistance

  • Intrinsic resistance. Some bacteria are intriguingly resistant to antibiotics, such as those that don’t build a cell wall (penicillin prevents cell-wall building).
  • Acquired resistance. Bacteria can acquire resistance through new genetic change or by transferring DNA from a bacterium that is already resistant. This is the issue we’re having today.

According to the CDC, the following bacterial strains have developed the most resistance such that they’ve been listed as urgent hazards:

  • Clostridium difficile. Causes severe diarrhea, especially in older people and those who have serious illnesses.
  • Enterobacteriaceae. These normally live in the digestive tract but can invade other parts of the body, like the urinary tract, and cause infections.
  • Neisseria gonorrhoeae. Causes gonorrhea, a sexually transmitted infection. In 2016, the WHO said gonorrhea might soon become untreatable. 


Why antibiotic resistance is growing

When antibiotics are introduced in a bacterial population, most of the population dies but some resistant bacteria may survive. These resistant bacteria will continue to proliferate despite the presence of the antibiotic. In time, their population will increase until it becomes comprised mainly of resistant bacteria. Credit: ReActGroup.

When antibiotics are introduced in a bacterial population, most of the population dies but some resistant bacteria may survive. These resistant bacteria will continue to proliferate despite the presence of the antibiotic. In time, their population will increase until it becomes comprised mainly of resistant bacteria. Credit: ReActGroup.

There are a number of factors that contribute to this growing health hazard. Among them we can mention:

  • self-medication;
  • hygienic habits such as the use of anti-bacterial soap which research suggests is useless but significantly contributes to the growing problem of antimicrobial resistance;
  • counterfeit drugs, particularly rampant in the developing world;
  • antibiotics for livestock;
  • infections acquired in hospitals and nursing homes, particularly in the developed world;

There’s no surprise in the fact that antibiotic resistance infections correlate with the level of antibiotic consumption. The more antibiotics a population consumes, the faster bacteria will adapt and become resistant. One huge problem is the mindless use of antibiotics. For instance, many patients request their doctors to prescribe antibiotics when there is no need for them, such as in the case of viral infections. Research shows that up to 15 million people in the United States go to the doctor for a sore throat every year. About 70 percent of these patients receive strep throat antibiotics but only 20 percent actually have strep throat, according to the IDSA.

Another problem is compliance with strict drug regimes. To be effective, antibiotics needs to be taken at least over several days and the scheduling needs to be respected on the clock yet many patients fail to follow these instructions.

Things are worse in some countries than others. For instance, in some countries, antibiotics are available without a prescription so the potential for self-medication abuse is huge especially if the patient is not educated about antibiotics. In the absence of a proper diagnosis, suitable antibiotic choice, correct usage, compliance, and treatment efficiency monitoring, self-medicating antibiotics can only exacerbate the mounting resistance problem.

Another issue lies with antibiotics for domestic animals, particularly livestock. Farmers widely use antibiotics to stave off infections but also for promoting growth. Approximately 80 percent of the antibiotics sold in the United States are used in meat and poultry production, and in the vast majority of cases, the antibiotics are used on healthy animals. This practice can lead to the evolution of ‘superbugs’ which can migrate into the environment as people consume meat.

In 2003, an Expert Workshop co-sponsored by the World Health Organization, Food and Agricultural Organization (FDA), and World Animal Health Organization (OIE) concluded “that there is clear evidence of adverse human health consequences due to resistant organisms resulting from non-human usage of antimicrobials.  These consequences include infections that would not have otherwise occurred, increased frequency of treatment failures (in some cases death) and increased severity of infections”

Most recently in 2012, the FDA stated “Misuse and overuse of antimicrobial drugs creates selective evolutionary pressure that enables antimicrobial resistant bacteria to increase in numbers more rapidly than antimicrobial susceptible bacteria and thus increases the opportunity for individuals to become infected by resistant bacteria.”

Solutions to antibiotic resistance

The sad reality today is that there’s not much we can do for patients who don’t respond to antibiotics, which is why mortality rates are so high.

“Antibiotic resistance is rising for many different pathogens that are threats to health,” said CDC Director Tom Frieden, M.D., in a statement. “If we don’t act now, our medicine cabinet will be empty and we won’t have the antibiotics we need to save lives.”

Some researchers have proposed alternatives to antibiotic treatment such as passive immunization or phage therapy but most efforts are directed towards the discovery of new and more efficient antibiotics. Like outlined earlier, however, most of our antibiotics have been isolated in the so-called ‘golden era’ of antibiotic discovery from a limited number of taxonomic groups, mainly from Actinomyces that live in the soil. Some research groups are exploring alternative ecological niches such as the marine environment. Other approaches involve borrowing antimicrobial peptides and compounds from animals and plants, as well as the natural lipopeptides of bacteria and fungi. There is also a potential to find new antibiotics by exploring the microbiota through the metagenomic approach. Finally, some groups are looking design new classes of antibiotics from scratch through complete synthesis.

Preventing antibiotic resistance

Finding new antibiotics, however, will likely not solve our growing antibiotic resistance problem. History has shown that after a new antibiotic therapy is introduced, sooner or later resistance will arise. This approach is destined to fail since bacteria will eventually respond to selective pressure by the emergence of resistance mechanisms.

What we can do, however, is to buy time until someone very clever figures a way to outsmart bacteria for good.

Scandinavian countries, for instance, banned the use of growth-promoting antibiotics in livestock since 2006 and other EU countries have been implementing similar measures. In 2012, the FDA ruled that certain extra-label uses of cephalosporin antimicrobial drugs should be banned from certain livestock.

It is estimated that in half of all cases, antibiotics are prescribed for conditions caused by viruses. Obviously, in such cases the antibiotics are useless and doctors and nurses ought to know better.

Governments have a critical role in combating antibiotic resistance. It’s imperative that robust action is taken both at a national and international level in order to regulate the appropriate use of quality medicines and education about the dangers of overuse. A lot of antibiotic resistance is building up in developing countries where there is little oversight. Governments need to work together to strengthen the health care quality in such places for the good of us all. Not least, the industry needs to move faster and more aggressively to research and develop new antibiotics.

What you can do

  • Don’t take antibiotics for a viral infection like a cold or the flu.
  • Do not save any antibiotics for the next time you get sick. Discard any leftover medication once you have completed your prescribed course of treatment
  • Always take antibiotics only after you’ve consulted with a health care professional. The FDA has a great campaign called “Get Smart: Know When Antibiotics Work”  that offers Web pages, brochures, fact sheets, and other information sources aimed at helping the public learn about preventing antibiotic-resistant infections.
  • Take an antibiotic exactly as the healthcare provider tells you. Do not skip doses.
  • Never pressure your provider to prescribe an antibiotic.
  • Never use antibacterial soap.
slomo sneeze

Physicists capture sneezing in slowmo, and this is actually important

slomo sneeze

Credit: Lydia Bourouiba

Lydia Bourouiba studies fluid dynamics at MIT and she says the seemingly simple act of sneezing has one of the most complex fluid physics. Aided by colleagues at her lab, Bourouiba used high-speed cameras to film volunteers while they sneeze. The results are mesmerizing shots of bodily fluids dancing in the air. Gross or art? That’s beside the point because slow mo sneezing might actually save some lives.

Bless you!

Besides being able to detect odors, the sensors that line the insides of the nose are very good at detecting foreign particles that might cause us harm. When these sensors detect irritant particles, they instruct the hair-like paddles that line the sinuses called cilia to move and expel the objects. A 2012 study published in FASEB Journal found that the burst of air produced by a sneeze not only clears nasal passages but also triggers the cilia sensors to kick the paddles into high gear for an extended period. What they say, essentially, is that a sneeze acts like a sort of reset button for the sinuses.

While sneezing is great to keep irritants such as germs, dust, pollen, animal dander, or pollutants from reaching the lungs and other vital organs, the expulsion also puts other people at risk. Respiratory diseases, for instance, often move from person to person transported by germs expelled through sneezing. If we can understand how a sneeze cloud moves, then we can be better prepared to contain risks, or at least that’s the thinking behind Bourouiba’s research.

“There’s a whole range of droplet sizes in this cloud, and the cloud is made of hot and moist air,” Bourouiba told NPR. “And it’s turbulent, so that means that it has swirls and eddies, and it’s moving very fast.”

One of the most revealing findings was that tiny droplets in a sneeze can travel through a whole room, in some conditions, in only a couple of seconds. The droplets can also remain suspended in the air for many minutes, the scientists reported in the New England Journal of Medicine.

“The largest droplets rapidly settle within 1 to 2 m away from the person. The smaller and evaporating droplets are trapped in the turbulent puff cloud, remain suspended, and, over the course of seconds to a few minutes, can travel the dimensions of a room and land up to 6 to 8 m away,” the researchers wrote.

So far, the volunteers Bourouiba has worked with were all healthy. The next step in her research is to enlist participants who are down with the flu and have them sneeze in controlled, hospital-like rooms.

The ultimate goal is to understand the physics of sneezing very well. This knowledge, coupled with germ theory and how respiratory diseases get transmitted between hosts, will enable scientists to design hospital rooms with just the right amount of moisture, ventilation, temperature and space so that risks are kept to a minimum.

And if you’ve ever wondered what’s the best way to keep your cold-ridden sneezes from infecting innocent bystanders, Bourouiba says the most effective technique is to sneeze on your elbow, not in your hand or fist. She says the elbow is the most effective part of the body in reducing a sneeze cloud’s momentum.


How many germs you can find in your home: about 9,000 different species

After they analyzed dust samples collected from 1,200 US households, researchers at University of Colorado at Boulder identified over 9,000 different species of microbes, bacteria and fungus. The exact makeup depends on where the home is located, the gender of the people living inside and whether or not pets are present.


Image: Red Beacon

What if I told you there were germs cramming every inch of your home? Most people are already aware of this, thankfully. Others freak out, partly because they might not understand that’s it perfectly natural this way. You weren’t affected by the germs until your heard the news, and you shouldn’t be after you find out. Nevertheless, there have been countless studies that document the germs living inside your home. This is, however, the most extensive by far revealing the extent of the biological makeup that comprises a typical American home.

The research is also another success story of citizen science coming to the rescue, as all the samples were collected by regular folks who then mailed them to the university. About 1,200 households responded to the call and sent dust collected from obscure locations people never usually bother cleaning, like the ledges above the door. The participants also filled out a questionnaire which asked what were their living and household habits, whether or not they were vegetarian, had pets and so on.

Some of the key findings:

  • The average American household has more than 2,000 different species of fungus and 7,000 species of bacteria.
  • Some of the fungus species include common strains like Aspergillus, Penicillium, Alternaria and Fusarium. 
  • Most of the fungus comes from outside the home so the fungus makeup of a home depends on where this is located.
  • Distinct bacteria were found in homes where only women or men lived. That’s because some types of bacteria are more common in women than men, and vice-versa. For instance, in male-dominant homes scientists found two types of skin-dwelling bacteria belonging to the genuses Corynebacterium and Dermabacter, as well as the fecal-associated genus Roseburia, in greater abundance than in female-dominant homes. The researchers attribute the difference in hygiene habits.
  • Having a dog or cat for a pet significantly altered the bacteria makeup of a home. In fact, having pets was the most influential factor that determine the biological ecosystem of your home. The researchers could determine whether or not dogs or cats lived in a home with an accuracy of 92% and 83%, respectively.

The researchers say that most of these microorganisms and fungi they identified are harmless.

“People do not need to worry about microbes in their home. They are all around us, they are on our skin, they’re all around our home – and most of these are completely harmless.

“It is just a fact of life that we are surrounded by these microbes,” concludes Dr Noah Fierer, associate professor of ecology and evolutionary biology at University of Colorado at Boulder.


Instead of counting the seconds it's been on the floor; it's just safer if you'd wash that hot-god or, better yet, start off fresh.

The ‘five seconds rule’ has been debunked

Instead of counting the seconds it's been on the floor; it's just safer if you'd wash that hot-god or, better yet, start off fresh.

Instead of counting the seconds it’s been on the floor; it’s just safer if you’d wash that hot-god or, better yet, start off fresh.

You just invested a lot of time, ingredients and love in that perfect sandwich, only for it land on the kitchen floor. Darn it! The 5 second rule immediately pops in your head and you confidently retrieve it, comforting your despair. A team of researchers at San Diego State University, however, has found that the germs do indeed attach themselves to edible items within that amount of time.

For the study, they used carrots which they laid on various surfaces – each was cleaned to serve as a constant. They tested the popular 5 second belief on a countertop, a kitchen sink, a table, and both a carpeted and tiled floor surface. The researchers found that germs affixed themselves to the carrots within five seconds of contact with different surfaces, the countertop being found to be dirtiest surface, with the carpeted and tiled floors following closely in second and third place. Apparently, the 5 second rule has been disproved, a gist that shouldn’t have been too hard for us to spot.

According to a separate study, conducted in tandem with the present one, some 65 percent of parents admitted to implementing the five second rule in their homes. Officials at disease control and prevention warn about the dangers inherent in germs contaminating foods, and recommend cleaning the food that comes in contact with contaminated surfaces.


Rubbings hands after washing increases bacteria count

According to a newly published study, it seems that rubbing your hands together in a hand dryer actually leaves them coated with more bacteria than immediately after washing.

When you rub your hands, you bring a lot of bacteria to the surface from the pores of your skin,” says Anna Snelling of the University of Bradford, UK. Snelling conducted the research with 14 volunteers, on three different types of air dryers, instructing each volunteer to use the air dryer for 15 seconds. On each model, the volunteer had to rub their hands while drying, while on the second try they would just hold their hands still.

The study revealed that when volunteers kept their hands still, the dryers reduced skin bacteria numbers by around 37% compared to just after washing. But the count rose by 18%when volunteers rubbed their hands under one of the machines. Paper towels proved the most efficient, halving the bacterial count even though volunteers rubbed their hands, so if you do happen to use an air dryer consider scrubbing your hands with a paper towel, especially if you’re around sick people. [link to study]