Does this effectively confirm the hygiene hypothesis ?
The hygiene hypothesis suggests that a newborn baby's immune system must be educated so it will function properly during infancy and the rest of life.
I'm weighing the need for my (possible future) children to spend time in a 3rd world country with germs & allergens for a little bit, to avoid heavily sanitized environments throughout their early lives. That's against the increased exposure to diseases and terrible pollution.
clarification: This is ofc much easier to do when your family lives in said 3rd world country.
That's not quite the same thing, this is specifically about the allergen itself needing to be introduced vs. avoided. The "hygiene hypothesis" as you said is more a general idea that the immune system should be exposed to a wide variety of foreign or pathogenic material in early age.
The avoidance of allergens was a deliberate thing under prior advice, and/or them being less common in the diet to begin with, it's not really a matter of hygiene or cleanliness.
clarification: This is ofc much easier to do when your family lives in said 3rd world country.