The most likely explanation could involve the "hygiene hypothesis, " which suggests that improved sanitation methods and efforts to keep germs at bay may deprive young, still-developing immune systems from being trained to recognize and react appropriately to the right types of irritants.

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How can you possibly monitor all of it in a room of ten people, or many more, and do so in time to react appropriately?

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For example, many autistic people have to learn the meaning of facial expressions by rote so that they can react appropriately.

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