The chlorine chemical mix stuff used to keep swimming pool clean. It doesn't matter how well I shower afterward, within 8 hours and for the next few days I am going to have an irritated, itchy rash that varies in size. It has happened every time I went swimming in a pool, wherever it was, ever since I was about 9 or 10. At this point I just don't bother going in them any more and only swim in lakes and rivers and other fresh water.