The Environmental Working Group’s (EWG) 2015 Guide to Sunscreen has gone viral these past few weeks, and I have been asked about it by numerous friends who are surprised by the conclusions. People are shocked that the EWG names Neutrogena sunscreens as the number one sunscreen to avoid, despite this brand being dermatologist recommended, and the report labels two key sunscreen ingredients, among a list of others, as toxic: oxybenzone and retinyl palmitate. As a dermatologist in training, I think it’s pretty much my duty to explain the scientific data behind these claims. So don’t go rushing off to toss your Neutrogena sunscreens in the trash just yet.
The claim: acts as estrogen in the body, causes endometriosis in women, lowers sperm count in men
The truth: Oxybenzone, belonging to a class of compounds called benzophenones, is a UV-A and UV-B filter that has been used in sunscreens since the 1980’s. People became concerned due to studies done in rats and fish or in skin cells grown in petri dishes showing that oxybenzone affected hormone levels. One such study showing that rats that were fed this ingredient developed larger uterine weights which was thought to be from estrogenic effects of oxybenzone. First of all, humans and rats (or fish or skin cells grown in dishes in a lab) are VERY different, and extrapolating animal or cell data to humans directly is dangerous and requires further study. But another important point to note is just how much oxybenzone were the rats fed? A subsequent study found that it is nearly impossible for a human to apply as much oxybenzone-containing sunscreen to get an equivalent dose of what the rats took in orally (ie a human would have to apply sunscreen to 100% of the body everyday for 70 years straight to take in the same amount of oxybenzone those rats got). As the authors write, “…we hope that this analysis helps to place into perspective the doses reported by the in vivo study from which inappropriate conclusions have been drawn and considerable controversy has developed.”
But enough about animal data, which we know is difficult to apply to humans. What about data looking at the use of oxybenzone in actual humans? What we want is the gold standard in clinical testing: a randomized controlled trial in humans. A study published in 2004 had human volunteers apply oxybenzone containing sunscreen to their bodies daily for two weeks and researchers measured their hormone levels afterwards. They found no significant difference in hormone levels between the groups compared to the controls. Interestingly, this one study testing oxybenzone on humans was not reported anywhere on EWG’s website.
2). Retinyl palmitate
The claim: speed development of skin cancer when exposed to sunlight
The truth: Retinyl palmitate (RP), which is the form of Vitamin A naturally stored in human skin, has been called into question because of preliminary data from a series of unpublished studies done by the FDA between 2002-2009. One large study done in rats showed that rats with a certain percentage of RP application on the skin and then UV irradiation developed more malignant (read: cancerous) lesions. There’s a few problems with this though. In groups of rats receiving the highest amount of UV radiation, there was no difference between animals getting RP vs. nothing. That’s odd, because if you expect RP to cause skin cancer when exposed to UV radiation, then higher amounts of UV radiation should lead to more skin cancer. Also, these test rats were actually a special breed of rats that were more prone than normal rats to developing skin cancer to begin with! 82% of these special rats that didn’t get any RP on their skin still went on to develop cancer. So how can you be certain that the skin cancers found were from RP or if that rat would have gotten skin cancer anyways? The answer is you can’t.
As Dr. Wang and his colleagues from a prominent cancer center (Memorial Sloan Kettering Cancer Center in NYC) published in a highly ranked dermatology journal in 2010: “In conclusion, based on currently available data from in vitro, animal, and human studies, there is no convincing evidence to support the notion that RP in sunscreens is photocarcinogenic.”
3). Methylisothiazolinone (MI)
The claim: causes skin allergies
The truth: Methylisothiazolinone, or MI, is a widely used preservative in sunscreen. The EWR cites this paper as evidence that MI is an allergen in sunscreens made for babies; however, on actually reading this paper, the study done is merely a survey of how many brands in a drug store contain MI as an ingredient. There is no data looking at cases of skin allergies caused by MI. Also, the researchers in this paper report that “In cases of recalcitrant dermatitis … allergic contact dermatitis to MI…must be considered as a possible causative factor.” Boiled down, this means that in children with severe skin allergies for which no doctors can find any cause, it is worth considering MI as a possibility when everything else has been exhausted. As you can imagine, this does not apply to the majority of the population. However, as I mentioned above, there is no data actually linking MI to skin allergies.
The skinny: So, in conclusion, after doing a thorough dig into the scientific literature on these key ingredients in sunscreen, I am not convinced by and don’t agree with the EWG’s claims. Sunscreen application including ingredients such as oxybenzone and retinyl palmitate is still a proven way to protect your skin against skin cancer and aging, and the many benefits of sunscreen greatly outweigh any potential risks that are not proven to be real at this point.
So hold on to your products, folks! And don’t forget to use daily application of SPF 30 sunscreen to sun exposed areas. I’ll go over physical vs. chemical blockers in sunscreen in a later post!
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