This correlation is often referred to as the 'hygiene hypothesis' by researchers. The underlying cause is still being understood; you can find an article compar

This correlation is often referred to as the 'hygiene hypothesis' by researchers. The underlying cause is still being understood; you can find an article comparing two theories here [0]. [0]: https://www.nature.com/articles/nri35095579 https://www.nature.com/articles/nri35095579