Walk into any supermarket today and you will find entire aisles dedicated to killing germs. Hand sanitizers, antibacterial wipes, disinfectant sprays, even soaps labeled ultra or maximum strength. Cleanliness is a state of mind, not just a habit. Especially in the wake of the global impact of COVID-19, the idea of constantly sanitizing everything around us feels not only normal, but responsible. But here’s a question gaining some traction in public health and microbiology that seems to run counter to common sense: what if all this being too clean is secretly working against us?
The human body is not designed to be sterile. It wasn’t. From the moment we are born we are colonised by trillions of micro-organisms, bacteria, viruses and fungi that live on our skin, in our mouths and most importantly in our gut. This community is known as the gut microbiome, and it’s involved in everything from digestion to immune function to even mood regulation. Rather than something we need to get rid of, many of these microbes are essential to keeping us healthy.
It’s not about being spotless, but basic hygiene like washing your hands before you eat or after you use the bathroom is key to stopping foodborne illnesses caused by pathogens like Salmonella infection or E. coli infection. The problem is the move from needed hygiene to constant, aggressive sterilization of our surroundings. And that’s when all surfaces are disinfected, all germs are bad, and we’re not exposed to the microbes we encounter on a daily basis. This might just start changing how our immune system develops and responds.
To see why, it’s useful to think about the way the immune system learns. Early and frequent contact with a diverse range of microbes helps the body learn to distinguish between harmless substances and real threats. This concept is commonly known as the “hygiene hypothesis,” a theory in immunology proposing that reduced exposure to microorganisms in early life may predispose to allergies and autoimmune diseases. The theory has changed over time, but the essence is the same: our immune systems need to interact with microbes in order to function properly.
This is what a typical day of a hyper-sanitized lifestyle looks like. Each morning we begin by washing up with antibacterial soap and disinfecting the kitchen counters and then fixing breakfast. Throughout the day, hands are washed often, surfaces cleaned, and public spaces treated with suspicion. Food is often handled in a similar fashion, pre-washed and pre-packaged, sometimes in the home in ways that are more sanitary than the minimum safety recommendations. These actions are understandable in a world where food poisoning and infectious diseases are real threats. But they also restrict the types of microbes we encounter.
By midweek, the effect of these habits is less about what we are avoiding, and more about what we are missing. Microbial diversity is a key player in gut health. A diverse microbiome is generally associated with better digestion, stronger immune responses and a lower risk of some chronic conditions. That variety can diminish when exposure to environmental microbes is reduced. Research has shown that people in more rural or farm-based settings, where exposure to soil, animals and natural bacteria is more common, tend to have more diverse gut microbiomes than those in highly urbanized, sanitized environments.
This does not mean that dirt is in itself good or that sanitation should be forsaken. Instead it emphasizes the importance of balance. The same environment that can introduce beneficial microbes can also harbor harmful pathogens. For example, mishandling of food, especially when foods are stored improperly or eaten after their safe limits, can cause infections from organisms such as Listeriosis. The aim is not to reduce hygiene standards but to avoid unwarranted over-use of antimicrobial products which interfere with both bad and good bacteria.
Another layer to this issue is how over-sanitizing impacts the gut indirectly via the use of antibacterial products. Many of these products don’t just focus on the harmful bacteria, they kill a wide range of microbes. If we overuse them, especially on our skin and in our homes, they can change the microbial environment we encounter every day. This can affect which bacteria ultimately colonize the gut, especially in children whose microbiomes are still forming.
By Thursday or Friday, thinking about food brings us back to the conversation about the intersection of safety and exposure. For example, fresh fruits and vegetables naturally harbor environmental microbes from soil and water. Rinsing well is essential to remove harmful contaminants, but use of strong chemicals or antibacterial agents is not recommended and can actually add new dangers. Again, not all of the food bacteria are bad. Fermented foods like yogurt, kefir, and kimchi also contain live cultures that can add beneficial bacteria to help promote gut health.
The tension between hygiene and contact with microbes is most apparent in our efforts to prevent disease. On the one hand, food poisoning outbreaks and infectious diseases emphasize the importance of strict hygiene practices. On the other hand, increasing rates of allergies, asthma and certain autoimmune disorders suggest something in our modern, ultra-clean environments may be changing how our immune systems work. It is not a simple cause and effect relationship but it is an area of ongoing research that still raises important questions.
It becomes clear in the course of this “investigation” that not all germs are the bad guys. The word itself has become a catch-all term that groups harmful pathogens and beneficial microbes, even though their roles in the body are completely different. To prevent illness, we need to eliminate exposure to dangerous bacteria, but we don’t want to (or can’t) eliminate exposure to all bacteria.
The idea of “being too clean” isn’t about blaming hygiene. It’s about understanding health is about interactions, not isolation. The gut microbiome loves variety, and that variety comes from the world around us, the foods we eat, the environments we pass through, and even the people we interact with. Too much sanitation can quietly diminish these interactions and alter the microbial landscape in ways that we are only beginning to understand fully.
Targeted practices are a balanced approach to hygiene. Hand washing at the right times (before eating, after using the bathroom or handling raw food) continues to be one of the best ways to stay well. To reduce the risk of foodborne disease, food should be stored properly, cooked at the right temperature and cross-contamination avoided. But other than those cases, constant disinfecting of clean surfaces or overuse of antibacterial products might not provide any additional benefits and could result in a decrease in microbial exposure.
By the end of the week the question of whether cleanliness matters is gone; it clearly does. The question is how much is sufficient. For decades, public health has been about reducing exposure to harmful pathogens, and that work has saved countless lives. Now there’s a growing recognition that part of the equation is supporting beneficial microbes, too.
The next time you reach for hand sanitizer or disinfectant wipes, it might be worth stopping to think about the context. Is this a time when you need hygiene to keep yourself from getting sick, or is this a habit created by the belief that all microbes are bad? This discrepancy is more important than it appears.
We are not designed to live in a sterile world. We are supposed to live in a balanced one, where exposure allows our bodies to work the way they were created to and cleanliness protects from harm. In that balance, the gut microbiome continues to do its quiet work, helping with digestion, immunity, and overall health in ways that are easy to overlook and impossible to do without.
Keeping clean is good for our safety. Being too clean, it could change what “safe” means down the road.
