'Most lipsticks are oil-based, so soften easily when heated.'

London - A chemical commonly used in lipsticks, face washes and toothpaste may cause heart and muscle problems, according to scientists.

They found triclosan, which is in hundreds of household products, can hinder the process by which muscles, including the heart, receive signals from the brain.

In tests on mice, they noted a “dramatic” 25 percent reduction in heart function within 20 minutes of exposure, and warned there is “strong evidence”it could affect human health.

However regulators and other experts insist triclosan levels in products are safe, and that the doses injected into the mice were higher than those to which humans would ever be exposed.

Although previous studies have found that triclosan may have links to thyroid and fertility problems, this is the first time its effects have been tested on muscles.

Scientists had thought that the chemical – which was devised to prevent bacterial infections in hospitals – was metabolised quickly by the body without harmful effects. However, the researchers at the University of California say it may remain active and be transported to organs, causing damage.

Professor Isaac Pessah, who led the study, published in the Proceedings of the National Academy of Sciences, said: “These findings provide strong evidence that it is of concern to both human and environmental health.

“For someone who is healthy a 10 percent drop in heart function may not have an effect, but if you have heart disease it could make a big difference.” His team injected a group of mice with triclosan. They saw a “significantly reduced” function in the heart’s left ventricle within 20 minutes.

Another test looked at the mice’s skeletal muscles by getting them to grip wire mesh. Those injected in the past hour had an 18 percent fall in their grip strength – although it was restored within a day.

By looking at muscle samples from mice in a test tube, the researchers believe the chemical disrupts the flow of calcium ions, which bring electrical signals from the brain to the muscles.

Under EU law, triclosan can be used in concentrations of up to 0.3 percent in toothpastes and cosmetics.

Dr Chris Flower, of the Cosmetic, Toiletry & Perfumery Association, said the study “did nothing” to undermine the safe use of triclosan. “It used doses of triclosan many times larger than the amount you’d get from using cosmetic products.” - Daily Mail