But among children, 15 % of clinical allergies are caused by unknown allergens that cannot be identified even by blood tests. Known as "internal allergies," their cause is unknown, but it is suspected that it is related to a hyperfunction of the nervous system.
而且，臨床上約有百分之十五的過敏兒童，即使驗血也找不到過敏原，稱之為「內因性過敏」，目前原因未明，懷疑與神經系統的過度亢進有關，病患只要碰到溫度、濕度的改變，神經系統就會分泌一些物質出來，影響免疫系統，進而產生過敏反應。