Chemicals in certain cosmetics have been found to disrupt hormones – with teenage girls particularly at risk.

This “hormonal disruption” could even increases the risks of cancer and other illnesses in later life, scientists added.

However, the good news is that this risk seems to lessen with reduced use of certain cosmetics.

A study found that those who took a three-day break from certain products saw a 45 per cent decrease in the level of dangerous chemicals in their body.

Lead study author Dr Kim Harley, of the University of California, Berkeley, said: “Because women are the primary consumers of many personal care products, they may be disproportionately exposed to these chemicals.

“Teen girls may be at particular risk since it`s a time of rapid reproductive development, and research has suggested that they use more personal care products per day than the average adult woman.”

The study decided to focus on teenage girls not only because they tend to use more cosmetics, but also because they usually purchase cheaper, mainstream brands - as opposed to ‘organic’ products with fewer chemicals.

The study had 100 teenage participants swap their regular cosmetics with alternatives labelled as free from chemicals - including phthalates, parabens, triclosan and oxybenzone (which are widely used in personal care products).

The study analysed urine samples from the teenagers from before and after the trial.

The level of a chemical commonly used in fragrances, called diethyl phthalate, declined by 27 per cent by the end of the trial, while other chemicals, called methyl and propyl parabens fell by 44 and 45 per cent, in turn.

Study co-author Maritza Cárdenas, a student at UC Berkeley, said: “One of the goals of our study was to create awareness among the participants of the chemicals found in everyday products, to help make people more conscious about what they`re using.

“Seeing the drop in chemicals after just three days shows that simple actions can be taken, such as choosing products with fewer chemicals, and make a difference.”

The researchers are now presenting the results to raise awareness of the dangerous chemicals - and hope that the restrictions on certain products will be tightened.

Dr Harley said: “We know enough to be concerned about teen girls` exposure to these chemicals.

“Sometimes it`s worth taking a precautionary approach, especially if there are easy changes people can make in the products they buy.”

The study was published in the journal Environmental Health Perspectives.

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