Why does my Apple watch occasionally cause a blood blister?

I don't wear it at night and it doesn't happen all the time. This is my 2nd watch over the years. It happened with my old watch as well. To cure it, I have to go without the watch for a few days or wear a bandage between the watch and my wrist. If it is a thin enough bandage, it doesn't interfere with the watch operation. After wearing an Apple watch for several years, the skin under the watch is now paper thin. That might be the cause of the blisters. I love my watch but this is starting to become a problem.