Kids should always avoid infection, but embrace the dirt

You know how it’s a good idea to expose children to colds, measles etc. as it makes them immune in later life? Turns out, not true. In fact, opposite:

In 1989, an epidemiologist in Britain, David Strachan, observed that babies born into households with lots of siblings were less likely than other babies to develop allergies and asthma. The same proved true of babies who spent significant time in day care. Dr. Strachan hypothesized that the protection came from experiencing an abundance of childhood illnesses.

Dr. Strachan’s original hygiene hypothesis got a lot of press, not only in the news media but in serious medical journals. Less publicized was the decade-long string of follow-up studies that disproved a link between illnesses and protection from inflammatory disorders like allergies and asthma. If anything, studies showed, early illness made matters worse.

Moreover, studies now show that the more infections a person has during childhood, the greater his or her chance of premature death from scourges of old age like heart disease and cancer. The link appears to be chronic inflammation, a kind of lingering collateral damage from the body’s disease-fighting response. [my emphasis]

But what about the original observation? Well, children raised around many other children are indeed less likely to develop allergies and asthma, but not for the reasons thought:

But the link isn’t disease-causing germs. It’s early and ample exposure to harmless bacteria — especially the kinds encountered living close to the land and around livestock and other young children. In other words, dirt, dung and diapers. Just as disease-causing microbes clearly bring on inflammation, harmless microorganisms appear to exert a calming effect on the immune system.

Got it. Don’t go nuts about hygiene, let kids play in the dirt and vaccinate, vaccinate, vaccinate.

More detail in the NYT article, which also points out that colds are not ‘natural’ and part of life as they’re only 5000 years old – nothing in evolutionary terms.

My new rule: never believe anything health-related unless it’s stated, directly, by a trained professional, and even then it’s not a bad idea to check it out with reputable sources online. And keep up with latest research.