> According to the World Health Organization, up to ⅓ of the global population suffers from allergic rhinitis,
Has anyone yet figured out why so many humans suffer from an allergy to many natural plants which we have lived around for millions of years?
It looks like the first documented case of Hayfever was March 1819[1], and at the time it was considered a very unusual and rare affliction. When and why has it now become so common?
There was a very interesting discussion recently on this topic. [1]
There are various hypothesis:
* changes to gut microbiome composition due to modern diets and overuse of antibiotics
* excessive cleanliness and hygiene. The "hygiene hypothesis" suggests that lack of exposure to diverse microbes leads to improperly trained immune systems
* increased exposure to chemicals, plastics, and pollutants that may disrupt immune function
* Cesarean sections and formula feeding rather than vaginal birth and breastfeeding
Exposure to cigarette smoke was also considered a candidate or reason, when I was younger. I haven't kept up with the thinking on or about this, but I believe it's still considered valid.
Remember, a few decades ago, a lot of the "Western" world smoked, including in public spaces and around kids. As I understand it, a lot of the rest of the world has caught up and still does so. And the Western world isn't exactly rid of the behavior, either.
P.S. I wonder whether anyone's studied possible multiple-generation, genetically-communicated knock-on effects of this.
P.P.S. "Pollen" is also a Racket language based blogging and authoring tool or environment. A bit sorry to see the name become overloaded.
Some allergies are triggered by a disease[1]. It is possible that hayfever is an outcome of a disease which has become common since 1819. The disease may have no other symptoms, and hay fever a symptom in only some people, and therefore be very hard to track.
> Has anyone yet figured out why so many humans suffer from an allergy to many natural plants which we have lived around for millions of years?
For those of us in the Americas most of us aren't living in the same places our ancestors lived for millions of years and so are living around a different set of plants than humans evolved with.
For example I've lived all my life in the western United States, about 30 years in California and 30 years in Washington.
According to DNA testing I have very little Native American ancestry, so it is very likely that almost all of my ancestors from more than around 300 years ago were not from here. The DNA tests say my ancestors were almost all British and German, so almost all of my ancestors from 600 or more years age weren't even on the same continent that I am.
How many generations does a population have to live in a new area before they adapt sufficiently so that the native plants don't give them allergic rhinitis?
> How many generations does a population have to live in a new area before they adapt sufficiently so that the native plants don't give them allergic rhinitis?
Assuming it is even hereditary, presumably it would also have to factor into reproductive selection (you mean runny noses aren't sexy?) for that to happen?
People often plant more male than female trees in cities to avoid having to pick up fruit, which perhaps doubles the pollen load. So it's a cultural problem that overlaps with the homelessness crisis, because the status quo applies pressure to keep everyone working within the system to feed themselves rather than adopting stuff like permaculture and no-till agriculture.
Also the immune system can get confused by two or more simultaneous stressors. So maybe a child has a cold while pollen is present, and develops too many antibodies to the pollen. I saw an animation once showing a normal immune system destroying cells covered in viruses. Then it showed a confused immune system destroying cells covered in allergen molecules. Which releases histamine and triggers a positive feedback loop. Multiple triggers may also be a root cause of many cancers, which can be thought of as autoimmune disease in the extreme. So for example, rheumatoid arthritis responds to methotrexate the way cancer does. Western medicine is often blind to this because it's too hard to do root cause analysis without large epidemiological studies, which are funded through the government and vulnerable to anti-government spending sentiment. Nobody wants to pay for it so we self-medicate rather than solving the underlying mystery.
In my case, I never had seasonal allergies until I was about 11-12, when my elementary school sprayed broadleaf herbicide to kill the dandelions. By coincidence, a family friend had me mow a lawn overtaken by dry cheatgrass, and all I had was a weed eater, so I was out for hours breathing the dust. From that day forward, I had flu-like symptoms for the entire month of May in my hometown, until I reached about 40 and grew out of it. I believe that the herbicide was the second stressor. So my quality of life was impacted by someone else's judgment call which categorized dandelions as weeds instead of, say, bee food. I finally found peace with this when I realized that saving the life of a child who is deathly allergic to bee stings is worth the other students suffering a lifetime of allergies.
I feel now that all questions that seem unanswerable, even with our considerable economic advantage, speak more about our cultural failings than our technological limitations.
Exposure, especially kids. Also food it I had to guess.
It seems that we are shielding ourselves ever more from exposure to nature. Which has tremendous benefits, but allergies seem to play into that.
As for food, I have now seen too many people cure themselves from hayfever and other allergies by ditching carbs, or other significant dietary changes. No accident if you ask me. And would line up somewhat with industrialization of food production post 1800 or so.
According to Wikipedia [0], Hayfever was already described in the 10th century. It is less common among people who grew up on a farm and more common with rising temperatures and air pollution. Hayfever is also significantly more common in urban areas.
Assumably all of these factors play a role in the prevalence today, though that doesn't rule out the existence of other undiscovered factors (e.g. a disease, as some people speculated).
In addition to other answers, I’d speculate there’s no strong negative selection against moderate allergies. There might simply be no evolutionary disadvantage to being slightly itchy and having running nose for H.sapiens.
Has anyone yet figured out why so many humans suffer from an allergy to many natural plants which we have lived around for millions of years?
It looks like the first documented case of Hayfever was March 1819[1], and at the time it was considered a very unusual and rare affliction. When and why has it now become so common?
[1]: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3110966/#:~:tex...,