# Modernity Has Made Us Allergic - Theresa MacPhail Synced: [[2023_11_30]] 6:03 AM Last Highlighted: [[2023_08_21]] Tags: [[Explainer]]  ## Highlights [[2023_08_22]] [View Highlight](https://read.readwise.io/read/01h8d46avy72n5pvnj7pef7cc2) > Nagler has [developed](https://pubmed.ncbi.nlm.nih.gov/27096316/) the “barrier regulation” hypothesis, which theorizes that our gut and skin microbiomes regulate what is and isn’t allowed into the body. Commensal bacteria on the skin and in the gut are integral to maintaining barrier function. Nagler explains that a single layer of epithelial cells is all that stands between us and our environment, making sure that what enters our bodies is either inhaled or ingested. [[2023_08_22]] [View Highlight](https://read.readwise.io/read/01h8d4aw6qmkpakzp59rdcnds3) > To Nagler, Elizabeth’s theory blaming antibiotics for her children’s food allergies isn’t so far-fetched. Changes in the gut microbiome in infants and children can lead to a greater risk of developing allergic responses as children age. And our children’s earliest environments are likely the most crucial [[2023_08_22]] [View Highlight](https://read.readwise.io/read/01h8d4d74t5s35d6b713hpk3r2) > So far, scientific evidence appears to back this up. Research by Rutgers University and the Mayo Clinic [found](https://pubmed.ncbi.nlm.nih.gov/33208243/) that children under age two who are given antibiotics are at greater risk for asthma, respiratory allergies, eczema, celiac disease, obesity and ADHD. The study looked at 14,572 children born in Olmsted County, Minnesota, between 2003 and 2011. If antibiotics were given in their first six months, the risk increased dramatically. [[2023_08_22]] [View Highlight](https://read.readwise.io/read/01h8d4erkdx8dnv62c96dpdgt4) > Finally, related studies of [Finnish](https://www.science.org/doi/10.1126/scitranslmed.aad0917) and [New York](https://www.science.org/doi/10.1126/scitranslmed.aad7121) babies [found](https://www.statnews.com/2016/06/15/antibiotics-c-sections-may-change-childs-health-for-the-long-term/) that C-sections and antibiotics correlated with altered gut microbiomes and a greater risk of allergies in childhood. > These findings don’t surprise Nagler. Vaginal births give infants what are known as “founder bacteria,” she tells me. As the baby moves through the vaginal canal, it is exposed to its mother’s friendly bacteria. Breastfeeding introduces more helpful bacteria into the infant’s gut. [[2023_08_22]] [View Highlight](https://read.readwise.io/read/01h8d4g5km0anttzfc7gzxs2jk) > Research has shown that babies born by C-section not only haven’t been exposed to the correct, harmless vaginal founder bacteria, but they have also been exposed to potentially harmful hospital bacteria. One recent review [found](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10146705/) that lactobacillus containing probiotics — the same bacilli found in breast milk — lowered SCORAD (Scoring Atopic Dermatitis) scores for children under age three who had moderate to severe atopic dermatitis, or more severe eczema. [[2023_08_22]] [View Highlight](https://read.readwise.io/read/01h8d4gk69qrmn1r90rvs0ayxm) > Breastfeeding for the first three months of life has also been [linked](https://pubmed.ncbi.nlm.nih.gov/32128903/) with a lower risk of respiratory allergies and asthma. In a study of 1,177 mother/child pairs, breastfed babies had a 23% lower relative risk of allergies by age six and a 34% lower relative risk of asthma if there was no family history of asthma. [[2023_08_22]] [View Highlight](https://read.readwise.io/read/01h8d4hdrm99r7w1d0vsh1pnf8) > But for children whose mothers supplemented breast milk with formula, the protective effect seemed to have mostly disappeared. (Important aside: If you’re a mother and you’re panicking a bit right now, please don’t. There are many valid reasons to have C-sections and to choose formula over breastmilk. A lot of this is complicated and there’s a lot that we still don’t know about these interactions.) [[2023_08_22]] [View Highlight](https://read.readwise.io/read/01h8d4kg6q0e8689kkqdfcpbr1) > A correlation was found between bacteria in bed dust and those found in the associated children; while the two populations of bacteria were not exactly synonymous, they did seem to directly affect each other. An increase or decrease in respiratory bacteria mirrored an increase or decrease in the bacteria in the infants’ beds. The [research](https://microbiomejournal.biomedcentral.com/articles/10.1186/s40168-020-00895-w) suggests that less frequent changing of bed linens may benefit the health of all our nasal and airway microbiomes. [[2023_08_22]] [View Highlight](https://read.readwise.io/read/01h8d4prch1c1qrmm4b6cj42mx) > The most compelling evidence that our 21st-century lifestyles and manmade environmental changes have spurred our allergies is this: Our companion species of thousands of years — dogs, cats, birds and horses — all get allergies regularly. Other species — those that do not live in our homes or alongside us — do not [[2023_08_22]] [View Highlight](https://read.readwise.io/read/01h8d52d2aa8kptg5f8cg5d1gd) > This tracks with research in humans that suggests that germ-ridden environments can also protect against allergies. [Children](https://pubmed.ncbi.nlm.nih.gov/28381231/) and adults who live with dogs have lower rates of asthma and obesity, in part due to more indirect exposure to bacteria that dogs carry and track into the home. A 2017 NIH-sponsored [study](https://pubmed.ncbi.nlm.nih.gov/28939248/) showed that exposing children in the first three years of life to high indoor levels of pet and pest allergens, like cockroach, mouse and cat allergens, lowers their risk of developing asthma by age seven. But whether exposure is protective, depends on the bacteria.