Children and the ‘hygiene hypothesis’

 Many parents and caregivers will be familiar with the so-called hygiene hypothesis, even if they do not know it by name.

It is essentially the idea that there is a link between the rise in allergic conditions and reduced exposure to microbes during childhood resulting from hygiene measures, such as frequent hand washing, introduced to protect children from infection.

Dr. David Strachan first proposed this link in an article that appeared in the BMJTrusted Source in 1989.

In a paper that appeared in the journal Perspectives in Public Health in 2016, Prof. Sally F. Bloomfield and colleagues examine Dr. Strachan’s original paper.

They write: “The immune system is a learning device, and at birth it resembles a computer with hardware and software but few data. Additional data must be supplied during the first year of life, through contact with microorganisms from other humans and the natural environment.”

They continue:

“If these inputs are inadequate or inappropriate, the regulatory mechanisms of the immune system can fail. As a result, the system attacks not only harmful organisms [that] cause infections but also innocuous targets such as pollen, house dust, and food allergens resulting in allergic diseases.”

Prof. Jonathan Hourihane, from the RCSI University of Medicine and Health Sciences in Dublin, Ireland, adds that the increases in eczema, asthma, hay fever, and food allergies over the past 30 years have likely resulted from decreased exposure to infections.

“We want to see children playing on the floor, getting dirty, and being exposed to lots of people in lots of environments,” he says. “The outcome of this is usually a strong immune system, linked to a healthy population of gut bacteria, called the microbiome.”

With this in mind, should parents of infants or young children be concerned about the effects of physical distancing and lockdowns on their immune systems?

Yes and no.