In this prospective birth cohort study, swimming did not increase risk for asthma or atopy.
Swimming has been recommended for patients with asthma because the warm humidified air might lessen exercise-induced bronchoconstriction, but several studies suggest that exposure to chlorine byproducts (especially trichloramine) might actually be asthmogenic. Researchers followed 5738 children in the U.K. from birth to age 10 years and prospectively collected data by questionnaire on swimming and respiratory status. Lung function, bronchial hyperresponsiveness, and skin tests were measured at age 7 to 8 years.
After adjustment for confounding variables, swimming frequency did not increase the prevalence of asthma, eczema, atopy, or rhinoconjunctivitis symptoms. On the contrary, swimming was associated with increased lung function and decreased prevalence of current asthma symptoms at age 10 years in children with previous wheezing. Swimming had a protective effect in children who wheezed before age 3.5 years.