A study conducted by Johns Hopkins Children's Center and funded by the National Institutes of Health supports the common "hygiene hypothesis" that some antibacterial chemicals and preservatives in hygiene products may make children more susceptible to food and environmental allergens. This is a highly debated topic in personal care, and there have been reports supporting both sides of the argument.
"Urinary Levels of Triclosan and Parabens Are Associated with Aeroallergen and Food Sensitization," which was published in the June 18, 2012 issue of the Journal of Allergy and Clinical Immunology, examined the relationship between the urinary levels of antibacterials and preservatives found in many hygiene products and the presence of IgE antibodies in blood using existing data from a national health survey of 860 children ages 6 to 18. The researchers investigated the antibacterial agents bisphenol A, triclosan and benzophenone-3 as well as the preservatives methylparaben, ethylparaben, propylparaben and butylparaben. They found that children with the high levels of triclosan and propylparaben in their urine were twice as likely to develop environmental allergies compared to children with low urine levels of those materials. A higher triclosan level in urine was also linked to food allergy risk.
The researchers concede that hygiene chemicals do not cause allergies but rather may play a role in immune system development. They imply that antimicrobial agents may disrupt the balance between good and bad bacteria, leading to an increased risk of allergies. This theory supports the "hygiene hypothesis" that pathogens are needed to build a healthy immune system and that a lack thereof could lead to immune system issues such as allergies.
The researchers are planning a long-term study in babies exposed to antibacterial ingredients at birth, following them throughout childhood.