Also getting the chlorine out of your own bathing water at home will home! You can buy a filter that goes on the faucet or in the tub! Also trying to use 'California Baby' products from Target work well!
I have the same problem. About 8 years ago I suddenly started getting a severe rash that would quickly spread over my whole body after being in public pools. ... even ones that used chemicals other than chlorine. I've found that the best thing to do is to make sure you keep your skin moisturized before swimming, and shower as soon as you get out of the pool (including shampooing your hair - i've gotten the rash on the back of my neck before because i didn't shampoo my hair and the chlorinated water was sitting on my neck the whole time). Also, mine is always worse when I sweat, so I would suggest not staying out in the heat or doing a lot of physical activity after swimming.
...lastly, going along with the heat thing....i don't suggest going into hot tubs. whenever i go into a hot tub i get a rash almost instantly.
after i have a rash the best way that i've found to treat it is just benedryl. if you don't want to deal with the drowsiness they make creams and sprays too.
my daughter to suffers after going in swimming pools. Started with rash in groin area and has got worse and now spreads all over her body.I have tried anti histamines and lotions to no avail, any other suggestions.
My sister gets the same rash from chlorine in pools. There is a newer pool treatment that does not contain chlorine. maybe you can find a public pool that uses it, and swim there. I do know that if she doesn't stay in too long, and showers right away, it's not too bad.