histamine
"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."
"Histamine is like the body's way of waving a red flag that signals that it doesn't like this substance. Histamine causes redness, swelling and inflammation. In mild to moderate reactions, it can cause the skin or back of the throat to itch."
"Histamine is like a directional signal for white blood cells and makes it easier for them to reach pathogens by making capillaries more permeable. Too much histamine makes the capillaries too permeable, however. Although the red blood cells are too large to squeeze through the openings created, fluid will leak out under the skin, ultimately producing hives. "
"So, the answer to part of your question is that histamine does NOT attack antigens. It would be the neutrophils that actually do that. Think of the histamine as being the manager/agent of the little dudes in the WBC bank. The histamine is like the dispatcher that sends the little dudes out to go and get the actual dirty work done. "
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