WHAT YOU SHOULD KNOW ABOUT SUNSCREEN Pt 2: Stability and Safety of Sunscreen Ingredients, both FDA Approved and Non-Approved

This is a continuation of the Sunscreen 101 Series.

In Pt 1: UVA rays vs UVB rays + the role of Antioxidants

In Pt 2 (this post):

    1. Why you should trust the FDA when they deem an ingredient safe

    2. Overview of FDA approved UV filters

    3. Should you use non-FDA approved filters?

    4. Overview of non-FDA approved UV filters

Here, we are going to cover UV filters (sunscreen ingredients) that are approved by the FDA and not approved by the FDA. Before we get into that though, let’s chat a bit about the FDA.

 WHY YOU SHOULD TRUST THE FDA ON SAFETY + WHY I CHANGED MY OPINION OF THE FDA

FDA approval is tricky business and one I do not fully understand. However, in the process of putting together this post (and wading through ungodly amounts of information about sunscreen ingredients), my opinion has changed quite a bit. Previously, my stance on the matter could be summed up in the two statements:

        1. The FDA hasn’t approved any new sunscreen filters because it is bureaucratic and slow 
        2. Chemical UV filters available in the US are not as stable, safe, or cosmetically elegant as ones available in Europe and Asia

Now, I understand that neither of these statements are entirely true. Let’s start with #1:

Turns out, there is a newly signed (in Nov 2014) Sunscreen Innovation Act that directly addresses the problem of the FDA being slow. It requires the FDA…

… to complete a review of a filed request and determine the safety and efficacy of the sunscreen active ingredient or combination of ingredients within 300 days for new requests or a shorter timeframe for requests pending before enactment of this Act.

Since the signing of this bill, the FDA has, in fact, reviewed and rejected a number of these filters, including Tinosorb S, Tinosorb M, and Uvinul T 150. The reason? Lack of clinical studies demonstrating long-term safety. Pointing to the fact people in Europe and Asia have been using these ingredients for years is not quite sufficient, and for approval, BASF, the producer of the filters, has indicated the requested clinical and preclinical testing could take another 5 years. On one hand, I am glad that the FDA seems to have robust standards for safety. On the other hand, I question whether or not the FDA’s standards and requirements are excessive if ingredients that have been approved by European Commission, KFDA, and other countries with highly sophisticated cosmetic markets and heath regulations fail to pass.

 Source

Moving on to statement #2:

There’s a lot of fear-mongering against chemical sunscreens that seems to be popular as of late. I’m sure most of it is well-intentioned, actually, but the amount of misleading information is pretty incredible. Take an organization like the Environmental Working Group. They aggregate results from various studies and spits out a safety rating for an ingredient. So far as I can tell, they are providing accurate information. The problem is they are providing sensationalist information to an audience in a way that the audience cannot adequately interpret.

For example, take the filter Padimate O. EWG gives Padimate O a rating of 5, indicating moderate hazard, and describes it as A derivative of the once-popular PABA sunscreen ingredient, research shows this chemical releases free radicals, damages DNA, has estrogenic activity, and causes allergic reactions in some people. 

Compare this with the information (readily available) on Wikipedia on Padimate O:

Padimate O absorbs ultraviolet rays, thereby preventing direct DNA damage by UV-B. However, the thus-excited padimate O molecule may then react with DNA to produce indirect DNA damage, similar to the effects of ionizing radiation. An in vitro yeast study conducted in 1993 demonstrated the sunlight-induced mutagenicity of padimate O.[1] The photobiological properties of padimate O resemble those of Michler’s ketone, which is considered photocarcinogenic in rats and mice. These findings suggest that padimate O might also be photocarcinogenic.[2]

However, multiple in vivo studies conducted in hairless mice following topical application of padimate O have demonstrated no carcinogenic effects and that padimate O reduces the number of and delays the appearance of UV-induced skin tumors.[3][4][5][6]

If you read part 1, you may remember my biologist friend’s stance on in vitro studies. If you haven’t, the takeaway is basically in vivo (in whole, living organisms) trumps in vitro (in test tubes). EWG is technically correct in its claim that research shows this chemical releases free radicals, damages DNA. However, the EWG not only fails to mention this research is an vitro yeast study, but also that there is an in vivo study that not only failed to produce any carcinogenic effects but also demonstrated Padimate O reduces the number of and delays the appearance of UV-induced tumors.

The nuances of in vivo vs in vitro studies, along with making sense of potentially conflicting findings from multiple studies and understanding how to extrapolate results from a study where mice were chronically fed a sunscreen ingredient to how that ingredient might affect humans, is not something most people can understand and interpret. Another sunscreen ingredient, oxybenzone, is a synthetic estrogen. One study shows that in rats, oxybenzone results in a 23% increase in uterine weight. However, in that study those rats were fed astronomically high doses of oxybenzone, which is a quite different treatment than applying 3% oxybenzone to one’s skin, and in humans there is no evidence that oxybenzone is harmful and significant buildup in our bodies is understood to be virtually impossible.

This is a good time to come circle to statement 1. Remember how the FDA denied approval of Tinosorb S, M, and Uvinul 150 T due to lack of research? Well, for a lot of the “controversial” FDA-approved sunscreens, there is a lot of research. Everything I’ve read indicates that the FDA approval process is exhaustive and that those studies linking UV filters with harmful results would have been taken into consideration. Let’s not forget that FDA approval is not a simple yes or no. With each approved filter, the FDA sets a limit of how much may be included in sunscreen formulations. You couldn’t get anywhere near the amounts of oxybenzone they used on those mice with enlarged uterines even if you tried.

Ok, now that’s out of the way, let’s review our FDA approved UV filters.

GUIDE TO FDA APPROVED UV FILTERS

Basically, I like tables so I made one that looks at whether an ingredient blocks UVA rays or UVB rays, if an ingredient is photo-stable, and if it interacts with other ingredients. More info is available if you click on the ingredients. Please note that photostability is relative. All chemical filters degrade when exposed to UV light. The ones considered photo-stable degrade slower.

*I am not a scientist and have compiled this chart to the best of my understanding. If there is any information you feel should be added or removed, please let me know!*

**About the inclusion of EWG ratings after I just talked about why they may be misleading: my general approach to interpreting them is this: if the score is low, then great. If it’s high, substantiate risks elsewhere or ignore. I wanted to include mostly for the non-FDA approved filters because even though they lack approval, a lot of them have low EWG ratings**

Ingredient Blocks UVA? Blocks UVB? Photo-stable? Interactions with other ingredients
Zinc oxide Yes Yes Yes  Degrades avobenzone if uncoated. Most sunscreens, with a few exceptions (i.e. Devita’s), coat their zinc oxide.
Titanium dioxide Limited Yes Yes Degrades avobenzone if uncoated.
Avobenzone Yes No No Degrades in the presence of octinoxate and uncoated zinc oxide, titanium dioxide, and black and yellow oxide particles. Almost all sunscreens use coated zinc oxide and titanium dioxide. Photostability can be improved if the following are added: enzacamene, homosalate, octisalate, octocrylene, oxybenzone, Tinosorb S, Tinosorb M, titanium dioxide (microfine), zinc oxide (micronized), diethylhexyl 2, 6-naphthalateOil Soluble
Mexoryl SX Yes No Yes Synergistic effect in protection when used with mexoryl LX; acidic and needs to be neutralized, usually with triethanolamine, in sunscreen formulations.Water soluble.
Helioplex Limited Yes Yes
Octinoxate No Yes No Photostability can be improved if the following are added: enzacamene, homosalate, octisalate, octocrylene, oxybenzone, Tinosorb S, Tinosorb M, titanium dioxide (microfine), zinc oxide (micronized), diethylhexyl 2, 6-naphthalate.Degrades avobenzone.Oil Soluble.
Octocrylene Limited Yes Yes Oil soluble. Has water-resistant properties
Oxybenzone Limited Yes Yes Stabilizes Avobenzone. Oil soluble.
Octisalate No Yes, but weak No Oil soluble. Has water-resistant properties
Homosalate No Yes No Improves photostability of other filtersOil Soluble
Padimate O No Yes No PABA derivative. Photostability can be improved if the following are added: enzacamene, homosalate, octisalate, octocrylene, oxybenzone, Tinosorb S, Tinosorb M, titanium dioxide (microfine), zinc oxide (micronized), diethylhexyl 2, 6-naphthalate
Ensulizole Limited Yes Yes Enhances SPF of the final productWater soluble
Dioxybenzone Limited Yes
Meradimate Limited No Oil soluble
Sulisobenzone Limited Yes Yes Helps stabilize other UV filters
Cinoxate No Yes
Trolamine Salicylate No Yes, but weak Used in water-resistant sunscreens

WHAT ABOUT NON-FDA APPROVED UV FILTERS?

Even though the FDA has not approved certain sunscreen filters, you may be interested in finding sunscreens that contain them for various reasons. Asian sunscreens (I’m particularly fond of Japanese ones) are known for their cosmetic elegance (no white cast, no stickiness) and European sunscreens are known for their high PPD (UVA protection) ratings. These desirable qualities are in part due to the greater variety of UV filters.

The most compelling reason, I think, to use non-FDA approved UV filters is the better UVA protection offered. In the US, UVA filters are essentially limited to Avobenzone, Mexoryl SX (very limited), and Zinc Oxide. I don’t find any of these options to be entirely satisfactory for different reasons. In the case of Mexoryl SX, the FDA has not actually approved the ingredient. Rather L’oreal, who has a patent on Mexoryl, managed to bypass the FDA sunscreen ingredient approval process using an expensive, backdoor approach to get specific sunscreens that contain this ingredient approved. This means the sunscreens in the US containing Mexoryl are very limited and expensive. Furthermore, Mexoryl SX is known to work synergistically with Mexoryl XL, which is not approved in the US. Avobenzone is great, but photo-stability is an issue. Helioplex is touted as being a very stable formulation due to the addition of oxybenzone, but is exclusive to Neutrogena. Lastly, zinc oxide is very stable, effective, and blocks the entire UVA range, which is fantastic in theory, except that it is extremely difficult to use the recommended amount of sunscreen with zinc oxide and very difficult to find a zinc oxide sunscreen that doesn’t leave a white cast. In fact, one study shows that people tend to apply less of physical sunscreens than chemical sunscreens (see Pt 1 for why it’s crucial to apply enough sunscreen).

Compare these with some filters available in Europe and Asia but were freshly denied by the FDA: Tinosorb S, Tinosorb M, and Uvinul A Plus. All three are highly stable and all three can, per Futurederm, can provide quite a bit of protection at a comparatively low %. Tinosorb is highly stable and, according to a 2007 study of sunscreen ingredients available in Europe, is the most effective filter for both UVA and UVB rays. Usually, physical blockers act as a shield and prevent UV rays from hitting your skin whereas chemical blockers allow the rays to contact your skin but convert the harmful UV light into other forms of energy (i.e. infrared light) that do not cause skin damage. Tinosorb has both physical and chemical sun filtering powers.

Uvinul A Plus, approved up to 10% in sunscreens in Europe, is a longwave UVA filter that is photo-stable and is great at boosting the UV protection of sunscreen formulations. Also, remember the claim about high protection at low concentrations? At a concentration of 3.5%, Uvinul A plus has three times the protective effect against the formation of free radicals than a formulation containing 3.5% zinc oxide.

Personally, the promise of better UVA protection and the fact these ingredients have been approved in both Europe and Asia is sufficient for me to overlook the lack of FDA approval in addressing safety concerns, but I am not a very risk averse person in general. It’s important to note that while I think Tinosorb S, Tinosorb M, and Uvinul A Plus are superstar ingredients, not all non-FDA approved UV filters are and I definitely recommend educating yourself as much as possible before choosing to use or not use a specific sunscreen ingredient. I’ve put together another chart with some information to get you started.

GUIDE TO NON-FDA APPROVED UV FILTERS

*I am not a scientist and have compiled this chart to the best of my understanding. If there is any information you feel should be added or removed, please let me know!*

**About the inclusion of EWG ratings after I just talked about why they may be misleading: my general approach to interpreting them is this: if the score is low, then great. If it’s high, substantiate risks elsewhere or ignore. I wanted to include mostly for the non-FDA approved filters because even though they lack approval, a lot of them have low EWG ratings**

Ingredient Blocks UVA? Blocks UVB? Photo-stable? Interactions with other ingredients Safety Information
Tinosorb S Yes Yes Yes Helps prevent photodegradation of avobenzone;
Has strong synergistic effects on SPF when formulated with Tinosorb M, Uvinul T 150, or Uvasorb HEB
No estrogenic effects in vitro
Tinosorb M Yes Yes Yes Helps prevent photodegradation of other UV absorbers, especially octinoxate No estrogenic effects in vitro
Mexoryl XL Limited No Yes Synergistic effect in protection when used with Mexoryl SX Low skin penetration
Uvinul T 150 No Yes Yes Low skin penetration. Approved to be used up to 5% in the EU and Japan
PABA No Yes Banned in Europe. All sorts of bad, including potential to cause photoallergy in and photosensitation shown in some human and animal studies, although results are inconsistent.
4-Methylbenzylidene Camphor No Yes Yes Oil soluble. May have estrogenic effect. Present in breast milk.
Disodium Phenyl Dibenzimidazole Tetrasulfonate Limited No Yes Synergistic effects with oil-soluble UVB filters.
Water soluble.
Low skin penetration. Approved to be used up to 10% in Europe, Australia, South Africa, Brasil and South Korea
Uvinul A Plus Limited No Yes May provide protection against free radicals. Best used in combination with Uvinul T150 Approved for use in the EU (up to 10%), South America, Mexico, Japan (up to 10%), and Taiwan
Uvasorb HEB Limited Yes Approved for use in the EU and Asia
Parsol SLX No Yes Yes Approved for use in the EU and Asia
Amiloxate No Yes Oil soluble. Approved for use in the EU and Asia

That’s it for now!

PS: You can see a quick rundown / comparison of all the sunscreens I’ve reviewed (mostly Japanese sunscreens) here.


 

SOURCES

In addition to sources linked in the post, here is the list of sources I used to compile this information:

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11 thoughts on “WHAT YOU SHOULD KNOW ABOUT SUNSCREEN Pt 2: Stability and Safety of Sunscreen Ingredients, both FDA Approved and Non-Approved

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