Hygiene hypothesis: don’t be too clean


Our lifestyle has shifted radically, from living in rural areas to living in cities. As we used to be exposed to a diverse range of bacteria, we are now accustomed to urban environments, preferably free from bacteria. We want to protect our children against germs and diseases, but are disinfected environments as healthy as we think? The hygiene hypothesis states that our modern sterile lifestyle confuses our immune system. Instead of protecting us from diseases, the immune system will respond the other way around, causing all sorts of allergic reactions and autoimmune diseases.

The human immune system is designed to fight off infections and harmful agents such as bacteria and viruses. Our change in lifestyle, from farm to city, means that we are less exposed to microbes in modern life. To become strong, our immune system needs to be exposed to a wide diversity of bacteria though.

Building the immune system starts after birth. When the baby is inside the mother’s womb, its immune system is very weak as the mother protects the baby. As soon as the baby is born, the immune system has to start working for itself and learn how to fight off infections and bacteria on its own. The more germs in every day life it is exposed to, the stronger it gets.

Children who grow up in over-sterilized environments don’t get the chance to properly challenge their immune systems. The immune system then can start attacking the body’s own tissues causing asthma or other autoimmune diseases. The immune system can also attack harmless particles in our environment causing allergic reactions such as eczema or hay fever. This happens in all developed countries where sterile environments don’t pose an effective challenge to a growing immune system.

How to change your lifestyle?

Rolling around in the dirt and having an unclean lifestyle is not the way we want to spend our lives. We still want to protect ourselves from harmful bacteria and viruses, but we shouldn’t exaggerate. Exposure to everyday microbes makes our immune system grow stronger. Walking barefoot on grass or exposure to bacteria of your close family members is not a bad thing. In fact, children who live with animals or who start attending day care early in life are exposed to a variety of microbes and are less likely to suffer from asthma and allergies. The way to go is to find a balance in what our immune system needs: not too many microbes but also not too little.

Do you want to know more about bacteria and the immune system?

Read our scientific article about how to maintain the bacterial balance by not killing all bacteria in your environment and in your body.

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