I recently chanced upon a TV ad for an "Immunity Boosting Hand Sanitiser", with school children using it as they were sitting down to lunch. It was a strange, almost paradoxical name, I thought, since the use of hand sanitisers and the presence of sanitised environments actually weakens your immunity.

We see bacteria as disease-causing bad guys and the market is full of various products that promise to keep us ‘protected’ by killing 99.9% of germs. In fact, the global market for hand sanitisers was about $654 million in 2013 and is expected to double by 2020.

But every inch of our bodies (inside and out) is covered in a "microbiota", often referred to as the microbiome – a community of trillions of bacteria, viruses and fungi that have evolved with us over millions of years. Our bodies carry as many microbes as they have cells and we would not function without these microbes.

The largest population and diversity of microbes in the human body are found in the gut. Interest in gut microbes is growing and studies have shown that apart from helping us digest food and processing nutrients, they also affect inflammation, hormones, obesity, skin, stress levels and brain function and mental health.

These microbes are not just harmless, we could not function well or even survive without each other. Here's more from NPR on how our microbiomes develop and the role they play.


The personal care chemical

Of course, not all microbes are beneficial, but our obsession to keep things sterile is doing more harm than good.

Most personal care products contain triclosan and triclocarban. There is a high chance you will find them in the ingredients of your toothpaste and hand wash. They are chemicals that were intended to be used as pesticides, but today are found in personal care products including soaps and toothpastes.

These chemicals are easily absorbed into the body – if it is in toothpaste, most of it is absorbed into the bloodstream. Triclosan is a proven hormone disrupter, can weaken muscles and cause a host of health problems in humans and also harm to aquatic life. At the same time, there is no proven benefit from using these anti-bacterial soaps as even the Food and Drug Administration in the United States has found. They are in fact, contributing to antibiotic resistance – exposing germs to low concentrations of antimicrobials is quite the textbook way of breeding resistance in them, much the way vaccines work. Studies have also shown that bacteria that become less susceptible to triclosan can develop "cross-resistance" to antibiotics.

Even anti-microbials and alcohol-based sanitisers that may not contain chemicals like triclosan have been connected to weakened immune systems, autoimmune disorders in which the body’s immune system attacks itself, increased allergies possibly due to reduced exposure to bacteria, antibiotic resistance in microbes, and hormonal imbalances. And, of course, when sanitisers do kill bacteria, they kill all the good bacteria that the body needs along with and bad bacteria that may cause harm.

To battle harmful bacteria, when the need arises all we need are antibiotics. But our indiscriminate use of antibiotics has led to the spread of antibiotic resistant bacteria in every part of the planet, and so we have fewer and fewer drugs in our arsenal to fight them with. As a result, these new resistant strains of microbes that cause common conditions like urinary tract infections, tuberculosis and even hospital acquired infections cannot be contained by any drug.

The importance of dirt

An important theoretical framework for the study of chronic inflammatory disorders, the Hygiene Hypothesis, states that the lack of exposure to infections and microbes in early childhood is associated with several chronic inflammatory diseases.

The Hygiene Hypothesis was initially proposed in 1989 to explain why hay fever and eczema were less common in children from large families. This is now supported by data showing that diseases like asthma, autoimmune conditions or even Type 1 diabetes are more common in the industrialized world than the developing world; these conditions have been seen also in higher income households in developing countries as they get more affluent and, perhaps, cleaner.

Dirt protects you in several ways. It allows your immune system to grow, exposing you to good bacteria, and is linked to lower inflammation later in life. Some soil bacteria can even make you happy.

Sure, you must wash your hands after using the bathroom, handling meat and changing diapers. But removing dirt and germs is just a mechanical action of soap and water, and antibacterial soaps are quite useless. Yet, there are ads mocking international hand washing protocol that says washing hands with any soap and water for 20 seconds is sufficient.

So no, you don’t need to break out the hand sanitiser every time you have shaken someone’s hand or have been in a public place. You don’t need to kill every germ on your house floor and you don’t need to wash your vessels with antimicrobial dishwash. Your kids do not need to wash their hands with antibacterial soaps every time they have been out or touched pets. Your kids really must play in the dirt.

But we know now what kids have perhaps always known. A little dirt is good for you.