"Histamine is like your mom: she cares about you and she wants to protect you. But sometimes she is overprotective even when it's unnecessary. Such is the case with seasonal allergies. The immune system is complex, but in simple terms, in certain people different pollens trigger the immune system (and histamine), which leads to a "fight" response in your body. Your immune system sends out all sorts of cells meant to fight off the foreign intruder (pollen), and this weakens you and causes the allergies."