I've heard things like early exposure, breast feeding, and mother's nutrition can help, but always got the impression that allergies are pretty random.
To be honest, this may have already happened, but it would take a generation to see the effects. There was a major breakthrough on this a few years ago. I first heard about it on an episode of Science Vs [1]. That was merely weeks after my second child was born. It was interesting to see the advice from the pediatrician a few months later. The American Association of Pediatrics updated their advice accordingly [2], and my kids' pediatrician handed out informational fliers calling out "this has changed," etc. Hopefully other pediatricians are also updating their advice and doing a good job of educating families.
Check out the Science Vs episode [1] if you want details. The gist of it is that in a controlled study, they found that introducing allergens early reduced the prevalence of allergies by 86% compared to avoiding allergens. This means old advice (what I was told with my first-born) about avoiding allergens could actually increase the risk. The Science Vs episode goes into details about what led researchers to look into this and possible explanations about the mechanism involved.
[1]: https://gimletmedia.com/shows/science-vs/2ohd7e
[2]: https://publications.aap.org/aapnews/news/12250/New-guidelin...
There has been a fair amount of research (but no solid consensus) on why allergy rates are increasing.
But AFAIK there have been fairly few attempts to try to use any of those competing hypotheses to devise preventive treatments whose effectiveness could be tested experimentally.
There is also a lot of evidence that SLIT and OIT are effective treatments for food allergies and most importantly that they are far more effective and safer when started very early, before 2 or even before 1 if possible. Early SLIT and OIT should be prioritized for research.
Plenty of papers listed here:
I have approximately no allergies but was exposed to a very diverse and not sterile environment from early on, with other siblings being similar. I have two brothers close to my age that did have significant and in some case deadly allergies, who were born and raised in the same environment.
Among my siblings, it is a completely mixed bag of sensitivity. Some were highly sensitive to many things, others were sensitive to almost nothing. If mere exposure to non-sterile environments was sufficient then we should all have had similar sensitivity to allergens but the variance in fact was quite high.
But not only that. If they already have the allergy, you can actually cure it by slowly building up exposure until they stop reacting to it.
Very important to note that not everyone can be cured this way, it can be dangerous even fatal, and under medical supervision only. Far too many people think they can cure their own allergy, allergies aren't "real," or cases of grandparents trying to YOLO fix their grandkid by putting small amounts of e.g. peanuts in their food and causing airway obstruction.
This research is, undeniably, exciting, but people overstate it and act like we could just roll it out to everyone with allergies and they'd disappear (and that everyone who still has allergies is "choosing" to). That isn't at all where the science is at today.
So, as someone who was exposed as a baby, and was pretty much doing maximal exposure therapy, you need to write better test cases.