People who grow up with younger siblings close to them in age are less likely to develop multiple schlerosis (MS) than are people without such siblings, a new study finds.
The finding supports the idea that sloppy kisses from baby brothers and sisters might fend off disease in later years. As such, it adds to evidence in support of the hygiene hypothesis, which holds that early, frequent exposure to infectious agents prepares the immune system to fight off diseases rather than to turn against a person's own tissues, as occurs in autoimmune diseases, say Anne-Louise Ponsonby of Australian National University in Canberra and her colleagues.
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