– Are there any long-term side effects to swimming in chlorine? Currently the answer is unclear, but according to Dr. Andrew Weil, M.D., “research suggests that children who swim frequently in chlorinated pools may have increased risks of developing allergies or asthma. The latest on this comes from a study in Belgium, which found that teens who spent more than 1,000 hours swimming in chlorinated pools had more than eight times the risk of developing asthma or allergies, compared to kids who usually swam in pools using a copper-silver disinfecting method.”