Question of the month April 2010: Nanoparticles

Dear Paula,

I’ve been coming across more and more information about the risks of nanoparticles in cosmetics. I am particularly concerned about repeated stories about the sunscreen ingredients titanium dioxide and zinc oxide. You’re an advocate for both, and I use a sunscreen that contains titanium dioxide based on your recommendation. I really like my sunscreen but don’t want to keep using it if the titanium dioxide is a problem. I suspect the titanium dioxide is using nanotechnology because it applies smoothly and doesn’t make my face look pale. Am I putting my skin at risk by continuing to use this product? Please shed some light on the scary-sounding nanoparticles.

Dear Sandi,

I understand your concern and appreciate this opportunity to set the record straight, at least as far as current research is concerned. Nanotechnology is about changing any material from its original size and making it much, much smaller. This technology is used in various industries, from medicine to agriculture to cosmetics. In the case of cosmetic products and over-the-counter drugs such as sunscreens, making particles nano-sized has two chief advantages: it can make the product more aesthetically pleasing (this is often the case with mineral sunscreens – making the mineral active particles smaller allows them to go on without leaving a noticeable white cast) and it can enhance penetration of certain ingredients, such as vitamins and other antioxidants.

Concerns have been expressed in the media, online, and by certain lobbying groups about the use of nanoparticles for cosmetic products in general, and in particular when it comes to using nanoparticles of titanium dioxide and zinc oxide as the active ingredients in sunscreens. What’s been reported about these benign sunscreen ingredients often sounds scary, with some reports going as far as stating that nanoparticles of these sunscreen actives reach the bloodstream and are potentially dangerous. Some articles about sunscreen nanoparticles have stated these can interact with sunlight and cause cellular damage to skin. As alarming as this sounds, this information is not supported by any legitimate published information and is without support from the medical world or the FDA.

Reviews of scientific data by major regulatory agencies have concluded nanoparticles of titanium dioxide and zinc oxide remain on the surface of the skin and in the outer dead layer (stratum corneum) of skin. They do not absorb into the bloodstream and do not affect living skin cells. Studies coming to these conclusions have tested these nanoparticles on healthy, intact human skin and on various types of human and animal skin samples.

Based on these conclusions and those of studies I have reviewed from toxicologists, the issue of nanoparticle risk from the mineral sunscreen actives is not a human health issue. There is no proof that these sunscreen actives absorb into skin. Actually, you wouldn’t want that to happen regardless of any potential risk because sunscreen actives need to remain in the surface layers of skin in order to protect it from UV damage. Personally, I don’t avoid the use of sunscreens that contain nanoparticles of titanium dioxide and zinc oxide, and I don’t advise family or friends to avoid them either.

In terms of the potential for titanium dioxide to generate free radicals in the presence of sunlight, it has been shown that adding antioxidants to the mix (whether in your sunscreen or those naturally present in skin) eliminates this risk. You can be assured that every sunscreen with titanium dioxide that I recommend contains antioxidants too!

(Sources for this information: http://www.tga.gov.au/npmeds/sunscreen-zotd.htm#pdf, Experimental Dermatology, August 2008, pages 659–667; Environmental Science and Toxicology, July 2007, pages 5,149–5,153; Critical Reviews in Toxicology, March 2007, pages 251–277; Skin Pharmacology and Physiology, January 2007, pages 148–154; and Skin Pharmacology and Applied Skin Physiology, September/October 1999, pages 247–256).

Interestingly, a study from Taiwan demonstrated that applying nanoparticles of titanium dioxide to pin-prick sites actually had an antibacterial effect in the presence of sunlight. The nanoparticles actually kept the wounded pin prick sites from becoming infected (Source: Artificial Organs, February 2008, pages 167–174)! This would not be the expected outcome if nanoparticles of titanium dioxide were inherently harmful to skin cells.