Nickel is the most common cause of allergic skin reactions, despite many barrier creams, anti-inflammatory drugs, and attempts to avoid nickel. Nickel-induced dermatitis takes the form of a red, itchy rash and affects millions of people worldwide.

Jeffrey Karp and colleagues, Harvard Medical School, Massachusetts, USA, have found that nanoparticles containing calcium could offer a safe solution to the problem. The team showed that a thin layer of glycerine emollient containing nanoparticles of either calcium carbonate or calcium phosphate, when applied to the skin, prevented nickel from entering the body. The nanoparticles capture the nickel ions by cation exchange and remained on the surface of the skin, allowing them to be washed off. The nanoparticles themselves were designed so that they cannot penetrate the skin and were made from materials that the US Food and Drug Administration designate as safe for human use.

• Nanoparticles reduce nickel allergy by capturing metal ions
  P. K. Vemula, R. R. Anderson, J. M. Karp,
  Nature Nanotechnol. 2011.
  DOI: 10.1038/nnano.2011.37