Swimming in chlorinated pools appears to increase the risk of developing asthma and hay fever according to new Belgian research.

Researchers studied 847 students between 13 and 18 years of age and found that allergy sensitive children were more likely to develop asthma and other allergies if they swam in chlorinated pools than un-chlorinated pools.

Those who spent more than 1000 hours in chlorinated pools were up to 14.9 times more likely to have asthma and 3.5 times more likely to have allergic rhinitis (Journal of Pediatrics).

Experts have suspected that the air quality around pools, particularly indoor ones, is to blame.

When the chlorine used to disinfect pools combines with swimmers’ sweat, saliva or urine, irritating chlorine byproducts are formed, and over time these chemicals may damage the airways.

Another more recent study led by Belgian researcher Alfred Bernard has also suggested that children who start swimming before the age of 2 may be at increased risk of a common infant lung infection, and possibly asthma and respiratory allergies later in life (European Respiratory Journal, 2010).

Dr Bernard did not advise parents to keep their young children away from pools, since it is an “enjoyable” way for kids to be active.

He said that parents should be sure not to over chlorinate their home pools and to try to avoid public pools that are heavily chlorinated.

Clues to watch out for, according to Bernard are an overwhelming chlorine smell and eye, skin and throat irritation among pool users.

Private pools should be kept it at the correct pH level to ensure they are not infected with waterborne diseases that thrive in water temperatures between 28 to 40 degrees. They should also be vaccuumed and have their filters cleaned regularly.

Removing chlorine entirely from private pools however is not advisable as inadequate sanitisation has been shown to cause significant illness and even death from pathogenic microorganisms.