What causes a skin rash in a swimming pool?

I have been taking water aerobics and have been breaking out with a skin rash at this last pool. Just wondering what may cause it. At the other pools which I have been to I never had a problem . They were indoor pools also. This one is a private indoor pool. The other ones were maintained by companies and two were for water therapy, one maintained by a hospital and the other two maintained by compainies that have several locations. I had no problems at their pools as stated.|||The chemicals are probably different from the other pools you have been in and you are sensitive to them.|||chlorine|||Could be that the chemical levels of the pool are too high for your skin to tolerate- make sure you shower after using the pool. I have had this happen myself as I have very sensitive skin.