Poison ivy itches because your confused immune system thinks your body is under attack. Consequently, killer T-cells in your blood stream release enzymes and toxins that lay waste to the surrounds. Fluid oozes from blood and lymphatic vessels, flows over skin, and kills cells�both good guys and those chemically bound to the sap�s active ingredient, urushiol. Your deadly T-cell liquid damages nerve cells and that makes you itch. |