Skin, Lip and Body Care

Shopping for Sunscreen-What About Oxybenzone & Nanoparticles?

+ CV Skinlabs Team

With the warmer weather, we’re all being reminded to protect our skin when we go outside. Not all sunscreens are equally safe, however.

I’ve talked about chemical sunscreens before, but today I want to focus on two particularly concerning formulas: those made with oxybenzone, and those made with nanoparticles.

Why It’s Best to Avoid Oxybenzone

Oxybenzone (also called “benzophenone-3”) belongs to a class of chemical compounds called “benzophenones” that are used in the printing industry, as well as in plastics, perfumes, soaps, and more. Oxybenzone is mainly a manufactured chemical, and is one of the most widely used sunscreens today.

What’s good about oxybenzone is that it offers broad-spectrum protection from both UVA and UVB rays, and it blends well in formulas. That means that it won’t create a white film on your skin when you rub it on.

But that’s about where the good stuff ends. Here’s why I prefer to avoid this ingredient when looking for sunscreen:

  • Potential hormone disruptor: A 2003 study on human breast cells found that oxybenzone displayed estrogenic and antiandrogenic activity. Several other animal studies have found that it has estrogenic potential, disrupting normal hormone function, and that its activity was compounded when combined with other sunscreen ingredients. How this might translate into humans is not yet certain, but since sunscreen does absorb into the body, it remains a concern.
  • Absorbs into the body: Speaking of absorption, a 2008 study found oxybenzone in over 96 percent of urine samples. Females were more likely than males to have concentrations above the 95th percentile.
  • Sensitizer: There are several ingredients on the market today that over time, can increase risk of an allergic reaction. Oxybenzone is one of these. In a 2006 study of 82 participants, oxybenzone was found to be the most common sunscreen allergen, causing contact dermatitis in over 25 percent of participants.
  • May damage skin cells: Like some other chemical sunscreens, oxybenzone has been found to form free radicals when exposed to UV rays. Theoretically, this sort of reaction could increase risk of premature aging and even skin cancer. A 1996 German study found that after topical application to the skin, oxybenzone was quickly photo-oxidized, meaning that it generated free radicals. Whether this would happen in real life is still unclear, and may depend on the sunscreen formulation. One might think the presence of antioxidants may help, but the same study also found that oxybenzone also inactivated important antioxidant systems that might have protected against free radical damage. Researchers noted that oxybenzone’s “rapid oxidation followed by the inactivation of important antioxidant systems indicates that this substance may be rather harmful to the homeostasis of the epidermis.” We need more research, but again, this is a concern.
  • Linked to endometriosis: A 2012 study linked benzophenones with endometriosis. The study measured the amounts of these chemicals in the urine of 600 women who were tested for endometriosis, and found women who had the highest level of benzophenone-1 (which is a by-product of oxybenzone) had a 65 percent greater risk of having the condition.

For these reasons-and until we know more-I would recommend avoiding this ingredient.

The Concern About Nanoparticles-But Zinc Oxide Still Considered Safe

Used to be when you put on certain sunscreens, you ended up with white marks on your skin. So-called “physical” sunscreens-namely, zinc oxide and titanium dioxide, which are considered safer than chemical sunscreens-are white, chalky minerals that naturally reflect UV rays, but don’t look particularly attractive on skin.

To counteract this tendency and produce more invisible formulas, manufacturers broke the ingredients down into smaller particles. First we had micronized formulas, which were made by grinding larger particles into smaller ones, to create a smoother appearance when the cream was applied. Thinking smaller would be better, manufacturers went even further by shrinking the particles a little more.

  1. Micronized particles: These are typically between 0.1 micron and 100 microns.
  2. Nanoparticles: These are usually less than 0.1 micron in size, often around 0.015 micron or 15 nanometers in diameter.

At first, this new technology was considered a breakthrough, as finally everyone could use these safer sunscreen without fear of the ghostly look. Later, however, we started hearing about some concerns.

As we make these particles smaller, aren’t they more likely to absorb into the skin and into the bloodstream? Typically both sit on the surface of skin, where they block both UVA and UBV rays. But what if they get inside the body?

The Australian Education Union (AEU) stated in May 2011 that it was concerned about nanoparticles in sunscreen, and advised all education workspaces to refrain from using it. A 2010 laboratory study, also reported that zinc oxide nanoparticles could cause cell death, and a 2012 study suggested that zinc oxide, when present in nanoparticles, could also generate free radicals when exposed to UV rays.

There have been several studies, however, that have come up with different conclusions. In 2011, for instance, scientists found that ultra-tiny zinc oxide particles did not penetrate beneath the outermost layer of skin cells, so would be unlikely to increase free radical damage. An earlier 2009 study showed similar results, as did a 2007 study.

A 2009 report by the Australian government’s Therapeutic Goods Administration reviewed the studies available at that time, and also concluded that in 15 out of 16 studies, neither titanium dioxide nor zinc oxide were able to reach viable cells in the body.

The Environmental Working Group agrees, noting that sunscreen manufacturers can use “surface coatings” that actually reduce the potential for the formation of free radicals, and maintains that both of these ingredients “pose a lower hazard than most other sunscreen ingredients approved for the U.S. market.”

They make one exception however-spray or powder formulas that may be inhaled.

Since nanoparticles are so small, they can potentially be inhaled, where they may contaminate the lungs. “Inhalation of nanoparticles is dangerous for many reasons,” they note, and strongly discourage customers from using powder or spray sunscreens with physical sunscreens like zinc oxide and titanium dioxide.

Bottom Line

The EWG provides a great report on sunscreens here that you can use to find safe products. Overall, my recommendation are:

  • avoid oxybenzone and other chemical sunscreens
  • choose zinc oxide and/or titanium dioxide in cream or lotion formulas
  • be cautious with nanoparticle formulas-particularly in powder and spray sunscreens

What do you think of these two issues? Do you avoid oxybenzone? Please share your thoughts.

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“Study Finds a Link Between Sunscreen Ingredient and Endometriosis,” Women’s Health Research Institute Blog,

Hackenberg S, et al., “Zinc oxide nanoparticles induce photocatalytic cell death in human head and neck squamous cell carcinoma cell lines in vitro,” Int J Oncol. 2010 Dec; 37(6):1583-90,

Missouri University of Science and Technology. “Sunscreen ingredient may increase skin cancer risk.” ScienceDaily. ScienceDaily, 7 May 2012.

Optical Society of America. “Scientists use laser imaging to assess safety of zinc oxide nanoparticles in sunscreen.” ScienceDaily. ScienceDaily, 2 December 2011.

Marissa D. Newman, et al., “The safety of nanosized particles in titanium dioxide-and zinc oxide-based sunscreens,” Journal of the American Academy of Dermatology, October 2009; 61(4):685-692,

Cross S.E., et al., “Human Skin Penetration of Sunscreen Nanoparticles: In-vitro Assessment of a Novel Micronized Zinc Oxide Formulation,” Skin Pharmacology and Physiology 2007; 20: 148-154,

Colin Stuart, “Why sunscreens are in the nanotechnology safety spotlight,” The Guardian, December 22, 2011,

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