One view is that allergies can develop as the result of childhood exposure to certain irritants, such as dust or animal dander, while the immune system is not yet mature.
If the animal kingdom held a sniffing Olympics, dogs and rats would probably battle for the gold, leaving the rest of us in the dust.
如果动物王国举行一场嗅觉奥林匹克赛的话，狗和老鼠很可能为冠军而战，其它动物就望尘莫及了。
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One view is that allergies can develop as the result of childhood exposure to certain irritants, such as dust or animal dander, while the immune system is not yet mature.