Nanoparticles , so tiny that 2,000 would fit across the thickness of a human hair, could prevent the itchy, red rash millions suffer because of allergy to nickel in jewellery, coins and cell phones. Over 30 to 45 million people in the US alone and many more worldwide, are allergic to the nickel found in many everyday objects. However, even though some countries regulate the amount of the metal in certain products to limit exposure, there is no good solution to the problem, the journal Nature Nanotechnology reports. "There have been approaches to developing creams with agents that bind the nickel before it can penetrate the skin, but these are not effective in most patients and can even be toxic when the agents themselves penetrate the skin, as most do," says Jeffrey Karp, who led the study at Brigham and Women's Hospital, according to its statement. "People also sometimes coat their jewellery with nail polish to create a barrier between the skin and nickel ions, but this won't prevent all exposures, such as handling coins or wearing a watch," he adds. Karp, who also holds appointments through Harvard Medical School, Harvard Stem Cell Institute (HSCI) and the Harvard-MIT Division of Health Sciences and Technology (HST), is himself allergic to nickel. When applied to the skin in a cream, the nanoparticles efficiently capture the nickel, preventing it from making its way into the body. Further, the nanoparticles themselves were designed so that they could not penetrate the skin. The cream with its nickel can then be easily washed off with water.