Pregnant mothers who regularly attend swimming classes may be increasing the risk of their child developing an allergic condition.
Scientists believe that commonly-found airborne chemicals, such as chlorine from pools and compounds found in cleaning products could be behind the five-fold increase in inherited allergies during the past 50 years.
Exposure to these chemicals may be altering an unborn child’s immune system, leaving them more sensitive to conditions such as eczema, asthma and hay fever.
The warning comes from a report in the British Journal of Dermatology that looks at the growing prevalence of these ‘atopic allergies’.
One theory, known as the ‘hygiene hypothesis’, is that an excessively clean lifestyle has resulted in a generation of children developing immune systems unfamiliar with many germs.
As a result, when they are later exposed to new irritants their body is more likely to have an allergic reaction.
However, experts from the St John’s Institute of Dermatology in London and the University of Manchester are investigating whether exposure to everyday airborne chemicals ‘during critical windows of pregnancy/early-life development’ have also contributed to the rise.
‘High-level exposure to volatile organic compounds in the domestic environment either during maternal pregnancy or in early life, is associated with development of childhood atopic disease,’ says the report.
‘Similarly, sustained exposure to airborne chlorinated chemicals from swimming pools during childhood has been associated with the development of atopic allergy.’
Dr John McFadden, consultant dermatologist at St John’s Institute, said further investigation was needed.
‘We in the science world are still struggling to find the exact cause of this rise,’ he said. ‘We have not proved anything, we are not saying this is the cause, this is a hypothesis, but we do know we are using far more chemicals than we did 50 years ago, whether it is in personal care products or processed food.’
Dr McFadden said the findings should not change the advice currently given to soon-to-be mothers, but the link required further study.
‘It is conceivable, but not proven, that persistent low-dose exposure to chemicals can have some effect on the immune system,’ he said.
Expectant women are encouraged to continue exercising during pregnancy, and swimming is recommended by the NHS as water helps support their additional weight.
Elizabeth Salter Green, director of CHEM Trust, which campaigns against the overuse of manmade chemicals, said: ‘It is well known that the foetus developing in-utero is extremely vulnerable to chemical exposures.
‘Simply put, in-utero growth, including neurological wiring of the brain and the development of the immune system, rely on chemical messengers – hormones – being at the right level at the right moment of development.
‘Therefore the theory that our increasing exposure to worrying chemicals is [affecting] those natural chemical messengers, leading to alteration of immune response and development of atopic allergies, via cleaning products, personal care products and volatile chlorinated chemicals in swimming pools, is highly plausible.’
The research is the latest to blame chemicals found in everyday products such as washing-up liquid and shower gel for a surge in allergic reactions.