An additive found in many liquid hand soaps and other common household products has been linked to cancer in a new study.

Triclosan is an antimicrobial commonly found in soaps, shampoos, toothpastes and many other household items.

Despite its widespread use, researchers have identified potentially serious consequences of long-term exposure to the chemical.

Their study, published by the journal Proceedings of the National Academy of Sciences, shows that triclosan causes liver fibrosis and cancer in lab mice.

Liver fibrosis is where persistent inflammation causes fibrous scar tissue to form around the liver cells and blood vessels.

Over time, it can cause cirrhosis which in turn can make the liver stop functioning.

However the researchers stress the findings are also relevant in humans, due to the processes they observed while conducting the study.

Triclosan is already under scrutiny by the Food and Drug Administration (FDA) in the United States due recent reports that it can disrupt hormones and impair muscle contraction.

Experts are concerned because triclosan is now so widely used in a variety of toiletries and household cosmetics.

Studies in the U.S. have found traces in 97 per cent of breast milk samples from lactating women and in the urine of nearly 75 per cent of people tested.

Triclosan is one of the seven most frequently detected compounds in streams across the United States.

While it seems common sense that antibacterial soap can protect against from illness caused by bacteria, this is not what the evidence shows.

More than four decades of research by the U.S. government’s Food And Drug Administration, along with numerous independent studies, have produced no evidence that triclosan, the active ingredient in many antibacterial soaps, hand gels and wipes, has any health benefits over old-fashioned soap and water.

One basic problem is that antibacterial soaps specifically target bacteria rather than viruses. But it is viruses that cause the majority of illnesses, such as colds and flu.

The most effective scientifically proven way to keep bacteria at bay is regular hand-washing with ordinary soap, along with good food hygiene in the kitchen.

Antibacterial soaps may actually cause health problems, too.

Evidence shows children with prolonged exposure to triclosan over months or years have a greater chance of developing allergies, including peanut allergies and hay fever, according to studies in the Journal of Allergy And Clinical Immunology in 2012, and in Environmental Health Perspectives in 2011.

This may be due to the fact that youngsters who use antibacterial soaps and cleansers reduce their exposure to bacteria.

Some research also suggests that the additives in antibacterial soaps could contribute to antibiotic resistance, a growing public health problem.

Author of the new study, Dr Robert Tukey, of the University of California, San Diego School of Medicine, said the chemical posed ‘very real risks’ to health.

‘Triclosan’s increasing detection in environmental samples and its increasingly broad use in consumer products may overcome its moderate benefit.

‘[Instead, it may] present a very real risk of liver toxicity for people, as it does in mice, particularly when combined with other compounds with similar action.’

Dr Tukey and his colleagues found that triclosan compromised liver function in mice.

Those exposed to triclosan for six months - roughly equivalent to 18 human years - were more susceptible to chemical-induced liver tumours.

Their tumours were also larger and more frequent than in mice not exposed to triclosan.

The study suggests triclosan may do its damage by interfering with a protein responsible for detoxifying, or clearing away, foreign chemicals in the body.

To compensate for this stress, liver cells proliferate and turn fibrotic (hard and scarred) over time.

Repeated triclosan exposure and continued liver fibrosis eventually promote tumour formation.

Study co-leader Dr Bruce Hammock said: ‘We could reduce most human and environmental exposures by eliminating uses of triclosan that are high volume, but of low benefit, such as inclusion in liquid hand soaps.

‘Yet we could also for now retain uses shown to have health value, as in toothpaste, where the amount used is small.’

In May, a study directly linked common household chemicals with damage to human sperm for the first time.

The scientists said that the ‘ubiquitous’ chemicals in everyday products may be contributing to widespread fertility problems in the Western world.

The German and Danish researchers tested almost 100 everyday chemicals – and discovered that a third affected sperm.