A chemical found in Teflon non-stick coatings could raise the risk of allergies, researchers have said.
The scientists claim the product may prime the immune system to overreact to allergy triggers, or allergens, such as dust mites or animal hair.
Lab mice given the chemical - perfluoro-octanoic acid - before being exposed to an allergen suffered more trouble breathing than those exposed to the allergen alone.
The results suggest a possible explanation for the rising incidence of childhood asthma.
The acid is also used to make all weather clothing and stain-resistant fabrics and carpets.
The researchers at the National Institute for Occupational Safety and Health in West Virginia examined the immune responses of mice subjected to an allergen. They found that those exposed to the acid first were more likely to have a reaction.
The doses of the chemical given to the mice were considerably higher, however, than the levels humans are likely to be exposed to.
Perfluoro-octanoic acid has become so widespread over the years that almost everyone has it in their body, including newborns.
Although the concentrations in human blood are relatively low there are fears about the potential health effects. The acid can contribute to thyroid problems, immune changes and testicular, liver and pancreatic cancer in laboratory animals.