HI, Thanks for the query. I understand your concern. - Itchy rash after swimming could be allergic reaction to the chlorine added to pool water..may be the concentration of chlorine is raised in water. The management consists of washing all the chlorine off your body.. the earliest. Use of swim spray is helpful. Vitamin C helps in relief. Anti allergic drugs over the counter Like Cetrizine can be taken at bed time, When the reaction is strong& there is no relief... you need help of an allergy specialist. - Swimming in natural water sources( pond, lake, river, sea).. the rash can be due to allergy to certain parasites thriving in body of birds / snails. Such allergy responds to steroid skin cream. over a weeks time. No relid needs specialist s treatment. Thanks.