Is the Hygiene Hypothesis True?

[BootinUp]

Published October 25, 2022
By Caitlin Rivers
Johns Hopkins Bloomberg School of Public Health


Did Covid shutdowns stunt kids' immune systems?

The hygiene hypothesis is the idea that kids need to be exposed to germs in order to develop healthy immune systems. We know that many common viruses did not circulate as widely during the pandemic, thanks to social distancing, masking, and other COVID mitigation measures. Are there downsides to those missed infections?

In this Q&A, Caitlin Rivers speaks with Marsha Wills-Karp, PhD, MHS, professor and chair of Environmental Health and Engineering, about the role of household microbiomes, birth, and vaccines in the development of kids’ immune systems—and whether early exposure really is the best medicine.

This Q&A is adapted from Rivers’ Substack blog, Force of Infection.

I THINK THERE’S SOME CONCERN AMONG PARENTS WHO HAVE HEARD ABOUT THE HYGIENE HYPOTHESIS THAT THERE IS A DOWNSIDE TO ALL THOSE STUFFY NOSES THAT DIDN’T HAPPEN [DURING THE COVID-19 PANDEMIC]. ARE THERE ANY UPSIDES TO VIRAL INFECTIONS? DO THEY HELP THE IMMUNE SYSTEM IN SOME MEANINGFUL WAY?

I don’t think so.

You mentioned the hygiene hypothesis, which was postulated back in the ‘80s. German scientists noticed that families with fewer children tended to have more allergic disease. This was interpreted [to mean] that allergic disease was linked to experiencing fewer infections. I have explored this idea in my research for a couple of decades now.

This phenomenon has helped us to understand the immune system, but our interpretation of it has grown and expanded—particularly with respect to viruses. Almost no virus is protective against allergic disease or other immune diseases. In fact, infections with viruses mostly either contribute to the development of those diseases or worsen them.

Continued https://publichealth.jhu.edu/2022/is-the-hygiene-hypothesis-true

[PoindexterOglethorpe]

1. I suspect that the main reason I am so very healthy

is that I got sick A LOT when I was a little kid. Third of six children. Spent the first seven years of my life in a low-income housing development with lots and lots of children, and we all played together. Very few childhood immunizations back then so I got all the then-usual childhood diseases. I was 5 when the polio vaccine came out. I got influenza several times growing up, including the Asian flu. I don't bother with the flu vaccine and the last time I think I got flu was about 50 years ago.

Our immune system is designed to be challenged by diseases, and when we recover we generally have immunity to that disease.

[BootinUp]

2. Based on anectdotal evidence, and it makes sense,

but the reality is you don't have enough facts to arive at a reliable concusion.

[PoindexterOglethorpe]

6. While you are right that my personal experience is hardly

something to assume any kind of general conclusion, it's still real. And valid.

For one thing, there's information out there that raising children with pets helps improve their immune systems. Also, overall, our immune system is designed to allow us to experience various diseases in our youth (the old childhood diseases of past eras) and then protect us from other diseases in adulthood. Typically, our immune system gets less effective as we get older. Sigh.

In my personal case, it seems as if all those illnesses I got in my youth and recovered from have really boosted my immune system. I last got flu around 1975 or so. I don't bother with a flu shot, although I might at some point change my mind about that. And I am not about to suggest anyone reading this should pass on a flu shot. I have gotten Covid shots and boosters, and unlike many I know who have done the same, I have not gotten Covid. It's possible that the fact I live alone and don't often see many other people is important here.

[oregonjen]

3. As a former preschool teacher

I learned that outside time and having the kids play in the dirt was extremely beneficial. Also, kids picking their noses and eating it (yuck!) was good, too.

I got sick for the first two years of teaching, but after that, maybe once a year. Preschools are the ultimate germ factory!

[BootinUp]

4. Not shown in the excerpt above are

related factors (not viral) and are understood to be important.

[PoindexterOglethorpe]

8. You got sick for the first two years, and after that maybe once a year.

A textbook example of how our immune systems are intended to work.

[muriel_volestrangler]

9. Nose picking is thought to be bad for you

Beta-amyloid is a protein believed to be a cause of Alzheimer's. According to the study published in Biomolecules, a peer-reviewed biological journal, the brain may produce this protein as a defense mechanism when pathogens are introduced via the nasal cavity.

“There is even some evidence to suggest that [beta-amyloid] may have antibacterial properties as a defense mechanism against microbial infections in the brain,” the report said.

So yes, dirty fingers going up the nose may trigger the brain to produce these dementia-causing proteins.

https://eu.indystar.com/story/news/2024/02/07/alzheimers-disease-neuroinflammation-nose-picking-dementia-memory-loss-hand-washing/72505363007/

Nose picking is associated with health risks such as spreading bacteria and viruses. It can also trigger nosebleeds and may cause damage to the delicate tissues inside the nose.

https://www.medicalnewstoday.com/articles/nose-picking#summary

Eating your snot is introducing the stuff on your fingers, not in your nose (the latter is already in you).

[progressoid]

5. This is interesting.

Unfortunately, as we saw during the pandemic, most internet "experts" who gained their knowledge from a few youtube videos, don't understand that there is a difference between bacteria and viruses.

[NickB79]

7. I always thought the hygiene theory was about exposure to non-infectious agents

Dirt, pollen, livestock, pets, etc.

Not viral infections.

[-misanthroptimist]

10. This stuff is way outside my knowledge base

What I do know is that I haven't been sick a single day since (I think) 1998. As a kid I grew up in a filthy house in a filthy neighborhood near a landfill -which we actually played in and picked through. I have no idea if any of that is relevant to my seeming immunity to Earth diseases, but it seems like a possibility to someone, again, with absolutely no expertise and little knowledge of medical issues.