The right sunscreen not only lowers skin cancer risk, it delays skin aging. For a sunscreen to effectively aid in photoaging prevention it must include active ingredients that protect against damage occasioned by long-wave length UVA rays. But some ingredients in some sunscreens actually accelerate skin aging, because they generate free radicals that attack cell structures and DNA, eventually resulting in chronic inflammation.
Your best protection against UVB/UVA rays can be found from formulations that use a combination of chemical UVB/UVA blockers. The two most highly recommended are Helioplex and Mexoryl. Using these chemical sunscreens are your best, and indeed only, way to protect your skin from aging damage caused by longer wavelength UVA rays.
Avobenzone is the only chemical UVA filter approved in the US. Unfortunately, due to the way absorbers work, it is highly unstable. When the avobenzone molecule absorbs photons of UVA light, electrons are excited into a triplet energy state. Without stabilizers the excited electrons will go on to either destroy the avobenzone molecule resulting in its quick degradation or, worst-case scenario, they get passed on to the lipid bilayers of the skin, resulting in lipid peroxidation damage via free radicals. If octocrylene is present it stabilizes avobenzone by accepting the “excited” energy.
How much UVA protection do chemical sunscreens provide? Let’s look at the two most widely respected formulations.
Helioplex –composition and concentrations:
- Avobenzone (3%)
- Oxybenzone (6%)
- Octocrylene (2.8%)
- Homosalate (10% in SPF 55 and 15% in SPF 70)
- Octisalate (5%)
In this formulation avobenzone is the UVA absorber, octocrylene stabilizes the avobenzone, and oxybenzone, homosalate and octisalate have been selected as the UVB absorbers. This combination eliminates the need for using octinoxate, the most potent UVB filter. Since octinoxate degrades avobenzone this formulation gets credit for getting that part right—not all of them do. Which is not to say it’s a great formulation.
The major drawbacks are:
- avobenzone only protects up to 380 nm—the UVA range is 400 nm oxybenzone—this UVB absorber generates free radicals, is associated with high rates of contact dermatitis, and is possibly photocarcinogenic; “believed to be a contributing factor in the recent rise of melanoma cases with sunscreen users.”
- Octocrylene—this photostabilizer and UVB absorber is associated with reproductive hazards and high rates of reported skin allergies.
- All chemical UV absorbers break down and generate free radicals after some amount of UV exposure, though the length of time varies. The every two hour rule must be observed. By the way, the two hour rule exists, not because sweating washes off the protection, but because the photoprotective properties of all chemical compounds degrade upon exposure to UV.
- Mexoryl SX –composition and concentrations:
- Ecamsule (2%)
- Avobenzone (2%)
- Octocrylene (10%)
- Ecamsule (2%)
In this formulation ecamsule, a benzylidene derivative, acts as a UVB/UVA filter. It has limited FDA approval for use in the US. Ecamsule protects against UV wavelengths in the 290–400 nanometer range, with peak protection at 345 nm. While it does not degrade as quickly as avobenzone it does break down, losing 40% of its protective properties after a couple of hours of exposure. Photostability and UV coverage are improved with avobenzone and octocrylene.
The major problem with this formulation is a 10% concentration of octocrylene. High rates of skin allergies are associated with octocrylene, which has been termed an “emerging photo allergen.”
In this formulation octocrylene does double duty as a UVB absorber and stabilizer of avobenzone stabilizer. Not a good idea.
Use a non-nano zinc oxide-only sunscreen. Zinc oxide is photostable, protects in the UVA range up to and well past 400 nm, and is anti-inflammatory.
SPF 30 in a zinc oxide-only sunscreen indicates concentrations of zinc oxide sufficient for the metal to act as a ‘heat sink. ‘ This reduces the heat effect on the skin that helps limit skin aging via the heat induction IR route.
Sunscreens tinted with iron oxides protect against visible light damage, including hyperpigmentation.
Get additional UVA protection from oils in the carotenoid family. This study shows that they help prevent UVA-induced wrinkling.
A Formulator’s Perspective
You can see where the search for the perfect sunscreen presents many confounding obstacles. So far zinc oxide is the only FDA-approved sunscreen agent I am wholly comfortable using. While titanium dioxide does a better job of protecting against shorter UVB wavelengths than zinc oxide, this is because at that range it acts as an absorber rather than a reflector—thus exhibiting all the problems of energy transfers creating free radicals that you find with chemical sunscreens. I agree with organizations like the EWG and researchers Dr. Niels Jorgenson who advise against using chemical sunscreens, and add my own note of caution regarding titanium dioxide use. In my book TiO2 is primarily an absorber, and as such causes skin aging problems we’d probably rather avoid.
This leaves zinc oxide, and while zinc oxide is an excellent ingredient that makes the consumers’ job of avoid chemical sunscreens a lot easier the search for the perfect sunscreen continues.
A sunscreen that is SPF 30, non-nano zinc oxide only, and tinted with iron oxides, remains the best option available when it comes to limiting photodamage and photoaging. Add carotenoids for extra UVA protection and you’re ready for a day of summertime play.