When you next come into contact with the substance your body perceives as a threat, the custom-built IgE antibodies will recognize the allergen. And tell other cells to start the allergic reaction. This involves releasing different chemicals such as histamine.
The idea is to get rid of the intruder as fast as possible. Histamine is part of an inflammatory response to the intrusion. Various fluids and white blood cells travel to the site of the attack to help. This causes swelling and other typical symptoms of an allergic reaction. Histamine along with other chemicals gets the body to produce more mucus to flush out anything that doesn’t belong. It also causes itching to make you scratch the perceived harmful material off your skin.
An allergic reaction typically causes symptoms in your nose, lungs, throat, sinuses, ears, lining of the stomach or on your skin.