What are the origins of this idea?
In proposing the hygiene hypothesis, Strachan suggested that lower incidence of childhood infections could explain the 20th century rise in allergies. This was based on studies showing that larger family size appeared to protect against hay fever.
Strachan suggested that smaller families provided insufficient microbial exposure because of less person to person spread of infection – but also because of “improved household amenities and higher standards of personal cleanliness”
From this the notion that “we have become too clean for our own good” has arisen
Most experts now agree that the “hygiene” hypothesis is a misnomer.
Whilst the link between microbial exposure and inflammatory disease is probably correct, the idea that children who have more infections are less likely to develop allergies is now largely discounted.
This means that allergies are not the price we have to pay for freedom from infectious diseases
Respiratory infections can actually increase allergy risks
There is now evidence that childhood infections, far from protecting, actually increase the risk of allergies