Experts agree: contact with bacteria early in life prevents allergies

– May 17, 2019

The hygiene hypothesis postulates that due to improving hygiene and the decrease in childhood diseases, the human immune system does not react well to innocuous stimuli, which explains the increase in allergies, eczema and asthma in the industrialised world.

The hygiene hypothesis

On 20 September 2018, a debate about the hygiene hypothesis was held at ARTIS-Micropia in Amsterdam. Experts in the fields of microbiology, immunology and infection prevention debated the hygiene hypothesis with each other and 60 invited guests, using five propositions as a starting point. This week, the outcome of this debate was published in an article in the Dutch Journal of Allergy, Asthma & Clinical Immunology (Nederlands Tijdschrift voor Allergie, Astma en Klinische Immunologie, NTvAAKI).

Micropia debate based on five propositions 

The first three propositions were about the use of the term 'hygiene hypothesis', the extent to which the hypothesis can be confirmed or invalidated, and whether preventing allergies by administering micro-organisms is effective. The final two propositions addressed the questions of whether intensive contact with micro-organisms could prevent an overactive immune system and whether outdoor play or a certain diet could prevent allergies and inflammatory diseases.

During the debate, the idea was raised that the term 'hygiene hypothesis' could incorrectly suggest that hygiene is harmful to health, whereas the opposite is true: hygiene is extremely important in preventing the spread of infectious diseases. However, contact with a diverse range of harmless bacteria, particularly early in life, is important for building up our immune system. There are many factors that restrict this contact: little time spent in nature; an urban environment comprising asphalt and concrete; decreasing levels of bacteria in our food; the practice of Caesarean sections, which limits the transfer of bacteria from mother to baby; and the overprescription of antibiotics.

Others argued that the term 'hygiene hypothesis' should not be changed to a better term like 'biodiversity hypothesis', because hygiene hypothesis is now a widely-known term, and a new term might just lead to greater confusion.

There was a consensus on the expert panel about the importance of exposure to a wide variety of micro-organisms early in life to prevent an overactive immune system, but more research is needed before conclusions can be drawn about effective and practical interventions in our daily lives.

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