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A voter uses hand sanitiser before entering a polling station during the parliamentary elections in Sri Lanka last week. Photo: EPA

Explainer | Why washing hands and cleaning to kill the coronavirus won’t weaken your immune system

  • The belief that a high level of cleaning and personal hygiene weakens our immune system is a common interpretation of the ‘hygiene hypothesis’
  • But extra hygiene measures will not weaken the immune system, doctors say. On the contrary, they are vital in controlling the pandemic
During the coronavirus pandemic we are constantly being reminded to practise good hygiene by frequently washing our hands and regularly cleaning the spaces where we live and work.

These practices aim to remove or kill the coronavirus that causes Covid-19, and thereby minimise our risk of infection.

But there have been some suggestions using hand sanitiser and practising other hygiene measures too often could weaken our immune system, by reducing our body’s exposure to germs and with it the chance to “train” our immune defences.

The good news is, there is no evidence to suggest this will be the case.

Why do people think good hygiene is bad?

For healthy immune function, it is important that we are exposed to a diverse range of bugs in the environment, known as microbes. Most of these do not make us sick.

The belief that a high level of cleaning and personal hygiene weakens our immune system is a common interpretation of what is called the “hygiene hypothesis”.

The hygiene hypothesis is a theory that suggests a young child’s environment can be “too clean”, and they will not be exposed to enough of these microbes to effectively stimulate their immune system as it develops.

A girl plays on a flooded street after heavy rains in the Indian capital of New Delhi last month. The hygiene hypothesis suggests a young child’s environment can be ‘too clean’. Photo: Reuters

The argument is that this results in increased allergies, asthma and certain autoimmune disorders. But scientists have refuted this hypothesis in recent years, as research has shown there are multiple other reasons for the increased incidence of these conditions.

Importantly, being too dirty does not help our immune system either. It generally makes inflammation worse.

What is the immune system?

The immune system works to protect our bodies against things that threaten to make us sick – from harmful chemicals, to bacteria and viruses, to cancer cells.

It is made up of two lines of defence. The first is the “innate” immune system, which responds rapidly to a range of pathogens to fight infection and prevent tissue damage.

Next is the “adaptive” immune system, made up of immune cells that develop a more targeted or specific response to fight off harsher germs such as viruses. Adaptive immune cells work by recognising small parts of the virus on the outside of the infected cell and destroying them.

These cells then become what we call “memory cells”. The next time they encounter the same virus, they can eliminate it straight away.

This development of the immune system starts after birth and declines in old age.

What can weaken our immune system?

Some aspects of our modern lifestyle can weaken our immune system. These include:

  • A lack of sleep
  • Certain medications and the overuse of antibiotics
  • Low vitamin D levels
  • A Western diet rich in processed foods, and reduced consumption of fruits and vegetables
  • A lack of physical activity
  • Stress and anxiety

But there is no scientific evidence to support the notion that extra hygiene precautions will weaken our immune system or leave us more susceptible to infection by bacteria or viruses.

Microbes are everywhere: in the air, on food, and in plants, animals, soil and water. They can be found on just about every surface, including inside and outside your body.

The hygiene measures recommended during the pandemic will help curb the spread of the coronavirus and greatly reduce our risk of infection – but will not eliminate all microbes from our lives.

What does cleaning do?

Cleaning refers to the removal of microbes, dirt and impurities from surfaces. It does not kill microbes, but by removing them, it lowers their numbers and therefore reduces the risk of spreading infection.

In contrast, disinfecting refers to using chemicals, known as disinfectants, to kill microbes on surfaces.

A combination of cleaning and disinfecting is the most effective way to get rid of microbes such as coronavirus.

A man washes his hands at a public water station in Indonesia. Extra hand hygiene is an important infection control measure. Photo: EPA

Extra hand hygiene is of course one of the most important infection control measures.

We have been advised to clean our hands with soap and water for at least 20 seconds. If this is not possible, use hand sanitiser with at least 60 per cent ethanol or 70 per cent isopropanol.

Frequent handwashing, especially if a sanitiser is used, can disrupt the natural skin biome, which can lead to increased skin infections. This can be managed with the use of moisturisers.

But the extra hygiene measures will not weaken our immune systems. On the contrary, they are vital in controlling the pandemic.

If you are worried about your immune system, don’t stop washing your hands or keeping your house clean. Importantly, follow a healthy balanced diet, do regular exercise and look after your mental health.

Vasso Apostolopoulos is pro vice-chancellor for research partnerships at Melbourne’s Victoria University, where Maja Husaric is a member of academic staff. Maximilian de Courten is health policy lead and professor in global public health at the university’s Mitchell Institute. This article first appeared in The Conversation.