Octinoxate, also known as Octyl Methoxycinnamate, is one of the most used sunscreen agents in the world. Chances are we have all used a sunscreen with it at some point in our lives. But lately its popularity among consumers has slowly begun to fade due to claims that it can cause cancer and hormonal imbalance. Are these claims reliable and based on solid evidence? Let’s investigate:
What’s Octinoxate and what does it do?
Octinoxate is an ester formed from 2-Ethylhexanol and Methoxycinnamic Acid. Octinoxate absorbs UVB (but not UVA) rays, protecting skin from sunburn and UV light-induced DNA damage. However, according to smartskincare.com, “when exposed to sunlight octyl methoxycinnamate is converted into a less UV absorbent form (from E-octyl-p-methoxycinnamate into a Z-octyl-p-methoxycinnamate)”. This means it loses something of its effectiveness, but the problem can be partly solved by adding to the formula other UV blockers, such as Tinosorb M, that prevent this conversion.
Is Octinoxate carcinogenic and toxic for humans?
No. There is no evidence that Octinoxate can cause cancer or hormonal disruption or can be dangerous to human health in any way. So, where do these rumours come from? Well, there are some studies that show Octinoxate to be toxic, but these were conducted by feeding rats with high quantities of this ingredient, or by applying it on uterus and liver cells. Here’s an example. In 2004, scientists at the University of Zurich, fed rats Octinoxate and found it to disrupt their hormonal balance.
But these findings simply don’t translate to humans. We’re not rats, and none of us eats Octinoxate (at least I hope so). To prove that Octinoxate is toxic and carcinogenic when used in sunscreens, it should be tested in the exact way sunscreens are used (topical application repeated every few hours) and in the quantities used in these products. And there are just no studies that even suggest that Octinoxate in sunscreens is bad for our health.
Octinoxate can be absorbed by the body
In 2005, researchers in Australia have found traces of Octinoxate in the stratum corneum and epidermis 24 hours after it was applied on the skin. While this can sound scary, the scientists concluded that this amount was “at least 5-fold lower, based on levels detected in viable epidermal cells, than those appearing to cause toxicity in cultured human keratinocytes. It is concluded that the human viable epidermal levels of sunscreens are too low to cause any significant toxicity”. I would still recommend pregnant women and children to stay away from Octinoxate and opt for a physical sunscreen instead as the effects of this sunscreen agent on them haven’t been fully studied yet, but there’s no reason to believe that topical application of Octyl Methoxycinnamate would be harmful for adults.
Beware of sunscreens with Octinoxate and Avobenzone
Avobenzone is the most used UVA filter in Europe and the US and thus it is often found in sunscreens that also contain Octinoxate. However, the two don’t get along very well together. When exposed to sunlight, Octinoxate degrades both itself and Avobenzone, which is not a very stable ingredient itself. It would be too long to explain here how this degradation occurs, but if you’re interested you can check out John Su’s detailed post on the topic at Future Derm. Here, I’ll just say that, although this degradation can be slowed down by stabilizers such as Octocrylene, sunscreens with both Avobenzone and Octinoxate will lose their effectiveness more quickly than other sunscreens and thus need to be frequently reapplied throughout the day.
Products with Octinoxate
If you’d like to use a sunscreen with Octinoxate, make sure it also contains UVA filters different from Avobenzone, so that your skin is protected against the entire UV spectrum. A good option for oily skin is Elta MD UV Clear SPF 46 ($21.99 on Amazon), which contains Zinc Oxide 9.0%, Octinoxate 7.5%, plus Niacinamide and antioxidants to help prevent the signs of aging. Those with dry skin, instead, may prefer its more moisturizing cousin Elta MD UV Lotion Broad-Spectrum SPF 30 Plus ($30.00), which contains Octinoxate 7.5% and Zinc Oxide 7.0%. Another good option is Blue Lizard Australian Sunscreen Daily Moisturizer Face SPF 30+ ($11,55). It contains Octinoxate 5.5%, Zinc Oxide 8%, as well as a bunch of antioxidants, including Green Tea Extract and Vitamin E.
The Bottom Line
Octinoxate is a safe, non-toxic and non-carcinogenic sunscreen agent that protects skin against UVB rays and helps prevent sun damage. However, to provide broad spectrum protection, it needs to be used with UVA sunscreen filters (but not avobenzone, which it degrades) such as Zinc Oxide.
Do you use sunscreens with Octinoxate?