Are we too clean? - the hygiene hypothesis misnomer
Since publication of the so-called hygiene hypothesis in 1989, IFH has constantly reviewed the evidence to better understand the implications for hygiene and cleanliness. It has become apparent that in the future, we will need to view the microbial world we live in very differently. Getting the public to see hygiene as part of a healthy lifestyle which combines effective hygiene behaviours, with behaviours that reconnect with essential microbes could have a huge impact on the burden of both these diseases and the development of sustainable health.
This website area contains a range of reviews and learning materials which address this issue.
Since 2020, this has been the most frequently asked question referred to the IFH website. The public are concerned that reduced exposure to “harmful germs” due to social distancing and lockdowns during the COVID-19 pandemic is weakening our immune systems, fearing that once we return to a more normal lifestyle, we will be more susceptible to colds, flu and other infections.
This 2022 review summarizes current understanding of how microbes interact with the immune system. Getting the public to regard hygiene as part of healthy lifestyles which combines effective hygiene behaviours, and behaviours that reconnect with essential microbes could have a huge impact on the burden of both these diseases and the development of sustainable health.
Fundamental to this is persuading the public that there is no conflict between these 2 aims. Whilst reduced exposure to harmful microbes may have some impact on the innate immune system, this should not “weaken” its ability to respond to new infection threats.
This 2019 report calls for an end to the myth that people are being too hygienic for their own good. The report addresses growing evidence that exposure to “good” microbes through contact with our human, animal and natural environment is essential for health. Failure to maintain a diverse microbiota on and in our body is being linked to an increasing range of diseases including allergic (asthma, eczema, hay fever, food allergies) and autoimmune diseases (such as multiple sclerosis, type 1 diabetes and inflammatory bowel disease) which have risen dramatically, particularly in the last 50 years.
Since 1997 IFH has been developing an approach to infection prevention in home and everyday life which has come to be known as Targeted Hygiene. Targeted Hygiene is key because it offers a lifestyle choice which maximises protection at times when we most risk exposure to harmful microbes, but at the same time maximizes ongoing interaction with microbial friends from human, animal and natural environments.
There is still a deep-rooted belief that a bit of dirt is good for you, but this persistent idea has led to confusion about the important role of hygiene to prevent infection. This paper describes a UK public survey that shows the need to change public attitudes to microbial exposure and the role of targeted hygiene.
The poll showed that 98% of people acknowledged the importance of hygiene with 50% agreeing that poor hygiene contributes to antibiotic resistance and 74% believing that hygiene is important to reduce pressure on the NHS. When respondents were asked to identify factors that prevent children coming into contact with bacteria which they believed beneficial to their child’s health, although 59% and 56% of people identified lifestyle factors such as using too many antibiotics and spending too much time indoors as causative factors, almost as many (55% and 52%) still hold the view that keeping homes too clean and using too many antibacterials are important. Less than one in five were aware that C-section rather than natural childbirth and bottle rather than breastfeeding were probable risk factor.
This easy to watch informative YouTube explains why sustaining “healthy” contact with our microbial world is vital to sustain a healthy microbiome in our gut, respiratory tract and skin. Failure to do this, because of lifestyle changes such as reduced contact with siblings, spending too little time outdoors etc., is now being linked to a whole range of diseases such as allergies and other immune disorders.
The YouTube also shows that good hygiene is not about keeping our homes and public spaces looking clean and free from dirt, it’s about what we do at the times in our daily lives when cleanliness really matters to prevent the spread of infection. This has come to be known as “Targeted Hygiene”. The YouTube demonstrates how to put Targeted Hygiene into practice to protect ourselves from infection, but also explains how Targeted Hygiene helps to ensure we still get exposure to essential microbes which we need to sustain health.
In this paper six experts in infectious and allergic disease review the burden of allergic and infectious diseases and the evidence for a link between microbial exposure and immunoregulatory disorders.
Evidence shows that interaction with microbes that inhabit the natural environment and human microbiome plays an essential role in immune regulation. Changing lifestyles and environmental exposure, urbanisation, altered diet and antibiotic use have had profound effects on the microbiome, leading to failure of immunotolerance and increased risk of allergic disease. The review concludes, however, that the term ‘hygiene hypothesis’ is a misleading misnomer as there is no good evidence that hygiene is responsible for the change in microbial exposures.
Evidence suggests strategies, including natural childbirth, breast feeding, outdoor activities, diet and appropriate antibiotic use, may help restore the microbiome and reduce risks of allergic disease. Promotion of a risk management approach to hygiene provides a framework for maximizing protection against pathogen exposure while allowing spread of essential microbes between family members. There is a need to change public, public health and professional perceptions about the microbiome and about hygiene.
This is a detailed review, carried out in 2012, of the scientific and epidemiological evidence relating to the so-called ‘Hygiene Hypothesis’. The 1989 ‘Hygiene Hypothesis’ originally proposed that lower infection rates in early childhood, transmitted by unhygienic contact with siblings, could be an explanation for rising levels of allergic diseases. It was suggested that this “infection” exposure no longer occurs because of higher standards of household and personal cleanliness – that “we have become too clean for our own good”.
Although microbial exposures are vital for immune regulation, the “Old Friends” hypothesis, first proposed in 2003, suggests that the required “exposures” are not infectious diseases (IDs), but environmental, and human and animal commensal microbes. This concept has now also been applied to a range of disorders such as multiple sclerosis, type 1 diabetes and inflammatory bowel disorders. New data suggests that altered exposure results from a range of measures vital to protecting us from IDs, but which have inadvertently reduced or altered exposure to the microbial friends that regulate our immune systems. These include food and water quality, sanitation and environmental cleanliness together with medical approaches such as vaccines, and antibiotic usage. The report concludes that, since the need for infection prevention is as great as ever, we need to tackle both issues – reversing the trend in inflammatory disorders and reducing the burden of ID. There is need for clearer communication about the Hygiene Hypothesis and guidance on how to target hygiene practices effectively.
This ‘Interactive Practical Guide’ explains, in plain language, our understanding of the so-called hygiene hypothesis and how and why reduced interaction with our microbial world is linked to rising levels of allergies and other chronic inflammatory diseases.
The guide also looks at how we can develop hygiene habits which will protect us against infectious diseases whilst at the same time maintaining exposure to the microbes which are important for our health.