Poison ivy is the scourge of summer. Get a little bit in one place, and it can spread all over your body. And it spreads over your body because your blood carries it there. Find out how poison ivy makes you blood a collaborator.
When you touch poison ivy, you pick up a chemical call urushiol. It forms an oil that's so potent that doses lighter than a grain of salt can cause blistering rashes. Once on the skin, it sinks in and binds to the cell membranes. Eventually it breaks down into a secondary chemical called quinone.
Quinone has an affinity for the white blood cells that your immune system rushes in to combat the foreign invasion of chemicals. It binds to the white cells, and uses them to spread throughout the body. After the first outbreak of pain and blisters, more and more outbreaks come as the quinone moves to new spots. The constant combination of damage and healing makes the outbreak itchy as well as painful.
It's surprisingly easy to combat poison ivy, at least if the problem is caught early. Steroids suppress the immune system, depriving the quinone of its ride around the body. They make the body incredibly susceptible to infection, so they won't work as a preventative measure, but going to the doctor immediately upon seeing the first outbreak can stop the whole process. So when you see a poison ivy rash, get a shot, and stop your immune system from collaborating with the enemy.
[Via With Poison Ivy, Timing is Everything, The Science of Supervillains]