A leading consumer association raised questions regarding the safety of tiny "nano" particles used in cosmetics. Nanoparticles are used in sun screens to block ultraviolet radiation, in emulsions to contain vitamins in face creams, and in other moisturisers to kill off bacteria. These products included nano emulsions - preparations containing oil and water droplets reduced to nano size - used to preserve active ingredients, such as vitamins and anti-oxidants, and for their lightness and transparency. Which? warns that there might be unexpected risk linked to use of nanotechnology.

Scientists have raised particular concerns about potential toxicity of fullerenes, a type of nanomaterial used in anti-aging cream. There is also a concern that the nanomaterials in sunscreens might be able to breach sunburned skin.

Which? asked various main as well as small cosmetic brands to give information about the use of nanotechnology, what benefits they thought it brought and how they ensured product safety. Only eight out of 67 cosmetics companies submitted information regarding the use of nanotechnology by them. Which? said that many companies are using nanotechnology without proper safety measures.

Sue Davies of Which? said: “We're not saying the use of nanotechnology in cosmetics is a bad thing, far from it. Many of its applications could lead to exciting and revolutionary developments in a wide range of products, but until all the necessary safety tests are carried out, the simple fact is we just don't know enough.”

Davies added that the government must introduce a compulsory reporting scheme for manufactured nanomaterials so we are all aware - and only those that are independently assessed as safe should be allowed to be used in cosmetics.