Dr Jenna Macciochi

So I think childhood is a real window of opportunity.

And this was kind of what sparked and partly sparked writing this book because I wanted to think about life course health.

And that's something we don't often do in research because it's really expensive to do a study of someone's entire life course.

So we tend to get a snapshot of one point in time.

And then we'll say that 25 year old male data is the same as someone in their 60s.

And it actually might not be.

But childhood is an interesting immune window because we have this rapid immune development that happens after birth.

And a lot of that is through exposures to germs.

Now, we used to have this idea that we had to have this kind of hygienic environment.

So we have in the 80s, the hygiene hypothesis emerged, whereby hygiene was associated with allergies.

And I think that was kind of misguided.

And the word hygiene is not the correct word.

That's later been updated to the old friends hypothesis by someone called Graham Rook.

at UCL in London.

And this posits that your old friends are the good microbes that live in our environment.

So we used to kind of think germs are bad, like germs are always causing infection, but actually 99% of the microbes around us in the air we're breathing on the surfaces we touch are harmless.

They're part of our environmental microbiome.

And then inside our guts, on our skin and our airways, we have our own microbiomes on our body.

And these are at these barrier surfaces.

And as I mentioned, a lot of your immune cells are also at the barrier surfaces and they communicate.