eli5: what happens on a cellular level when someone has an allergic reaction?
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This one is for anaphylaxis
Your immune system has made antibodies against something that wouldn’t cause infection. These antibodies (IgE) are attached to mast cells (a type of immune cell) and some other immune cells, but mast cells are the main one. When you are next exposed to the allergen, the antigen (the part of the thing you’re allergic to such as a protein) attaches to these antibodies. That then triggers the mast cells to release lots granules stores within them. These granules contain things like histamine, nitric oxide and other substances that are what cause the symptoms of anaphylaxis. Because there are such massive amounts of these substances and that they are in the blood so they get transported all round the body quickly you get a sudden and widespread effect.
These effects include causing airways to constrict. Blood vessels dilate (widen) and your blood pressure drops because it’s like trying to fill a much larger area with the same amount of fluid. You also get swelling of tissues (another reason bp drops as fluid moves out of the blood into the area of swelling).
It’s the immune system going into over drive
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