Reperfusion injury

Reperfusion injury happens when blood flow comes back to an area that was deprived of oxygen for a while. Imagine a little village with a river that dries out, and the plants and animals there start dying. Then, after some time, the river flows again, and suddenly all the remaining plants and animals get overwhelmed with a super large amount of water, and some may even drown. Something similar may happen in your body if there's a blockage in one of your blood vessels – like a clog in a pipe – that causes a part of your body not to receive enough oxygen. This lack of oxygen can cause cells to stop working or even die. When the blockage is removed, oxygen-rich blood flows back in, causing a massive reaction that can damage the cells even more. Think of it like this: when you're really thirsty, you take a big gulp of water, but sometimes it hurts your throat because you were so thirsty. Reperfusion injury is like that, but for your cells. It's not fun, but doctors try to prevent it from happening or minimize the damage when it does, just like you drink water slower or try to make it less cold when you have a sore throat.