Giulia Enders

bios means “for life.” Probiotics are edible living bacteria that can make us healthier. Pre bios means “before life.” Prebiotics are foodstuffs that pass undigested into the large intestine, where they feed our beneficial bacteria so that they thrive better than bad bacteria. Anti bios means “against life.” Antibiotics kill bacteria and are our saviors when we have picked up a pack of bad bacteria.

Cleanliness really was thought to be next (in importance) to godliness; people craved a sense of order in a life full of chaos. The anthropologist Mary Douglas summed this up in her book Purity and Danger with the phrase, “Dirt is matter out of place.”

This cannot be a good kind of cleanliness. The higher the hygiene standards in a country, the higher that nation’s incidence of allergies and autoimmune diseases. The more sterile a household is, the more its members will suffer from allergies and autoimmune diseases.

The aim of cleaning, then, should be to reduce bacteria numbers—but not to zero. Even harmful bacteria can be good for us when the immune system uses them for training

Bacteria get out of hand when they encounter the perfect conditions: a protected location that is warm and moist with a supply of delicious food. There are four recommended strategies for keeping them in check: dilution, temperature change, drying, and cleaning.

Kitchen sponges should only be used for cleaning the worst of the dirt off. Plates, cutlery, and so on should then be rinsed briefly under running water. The same is true for dish towels or drying-up cloths if they never get a chance to dry out. They are more useful for spreading a nice even layer of bacteria on your utensils than for drying them. Sponges and cloths should be thoroughly wrung out and allowed to dry—otherwise they become the perfect place for moisture-loving microbes.

Cleaning means removing a film of fats and proteins from surfaces.

In principle, we use the same system when we use hand cream. We trap microbes in a film of fat and hold them captive there. When we wash the film off, we rinse the bacteria away with it. Since our skin produces a natural coating of fat, soap and water are often enough to achieve this effect. Some of the fat layer remains, aiding its replenishment after washing. Too frequent hand washing makes no sense—and the same is true of too frequent showering. If the protective fat layer is rinsed away too often, our unprotected skin is exposed to the environment.

hese new ideas about the use of bacteria illustrate one thing very clearly: cleaning does not mean annihilating all bacteria. Cleanliness is a healthy balance of sufficient good bacteria and a few bad ones. That means smart protection against real dangers and, sometimes, deliberate contamination with good bugs.

Antibiotics can work in three different ways: by peppering the bacteria with holes, by poisoning the bacteria, or by rendering the bacteria unable to reproduce. They have no effect on viruses at all.