Tuesday, December 9, 2014
When used appropriately along with other photo-protective measures, sunscreen is effective in reducing the risk of melanoma (1) and nonmelanoma skin cancers (2).
Compared to the first commercial sunscreens that appeared in the United States in the 1920s, today’s sunscreens provide superior UV absorption profiles as measured by both the height (magnitude) and breadth (broad spectrum) of protection provided.
But to make a sunscreen effective, multiple factors must be considered and addressed.
UV Filters
Ultraviolet (UV) radiation filters are the active ingredients in sunscreen formulations. They shield skin from damage by absorbing and reflecting this invisible light. The U.S. Food and Drug Administration (FDA) has approved only 17 UV filters for use in domestically manufactured sunscreens, compared with many more advanced UV filters available to sunscreen manufacturers in Europe, Asia, and Australia.
Currently the FDA is reviewing eight new UV filters via the Time and Extent Application (TEA) process. Experts generally agree that these new actives can improve sunscreen efficacy, extending UVA protection beyond the 380nm range.
Active ingredients pending FDA approval via the TEA process.
| Active Ingredients | Maximum concentration | Peak Absorption λ (nm) | UV action spectrum |
|---|---|---|---|
| Methylene-bis-benzotriazolyl tetramethylbutylphenol (MBBT) (Tinosorb M) (Bisoctrizole) | 10% | 305,360 | UVB, UVA |
| Bis-ethylhexyloxyphenol methoxyphenyl triazine (BEMT) (Tinosorb S) (Bemotrizinol) | 10% | 310,343 | UVB, UVA |
| Ethylhexyl triazone (EHT) (octyl triazone) | 5% | 314 | UVB |
| Isoamyl methoxycinnamate (Amiloxate) | 10% | 310 | UVB |
| Methylbenzylidene camphor (Enzacamene) | 4% | 300 | UVB |
| Diethylhexyl butamido triazone (Iscotrizinol) | 3% | 312 | UVB |
| Terephthalylidene diacamphor sulfinic acid (Ecamsule) | 10% | 345 | UVB, UVA |
| Drometrizole trisiloxane (Mexoryl XL) | 15% | 303,344 | UVB, UVA |
Efficacy Enhancers
Selecting the type and concentration of UV filter to include in a sunscreen formula is only the first step in making a truly effective product, however; the choice of inactive ingredients plays an equally critical role.
Superior protection is provided by vehicles that dissolve and disperse the UV filters in a uniform fashion, delivering an even coating to skin topography. In addition to film-former technology (chemicals that ensure even spreading of the product on the skin), additives can be included to boost the UV filter efficacy by scattering the incident UV rays and increasing the length of their path to the skin (4).
Back to topPhoto Stabilizers
A shortcoming of many UV filters is their tendency to degrade following UV exposure. Avobenzone is a widely used long-range UVA filter that is inherently unstable and loses nearly 50 percent of its capacity after one hour of UV exposure (5), for example. Combinations of photostabilizers such as octocrylene and diethyhexyl 2,6 napthalate must be added to stabilize this agent.
Of note is that the landmark trial demonstrating the power of daily sunscreen use in dramatically reducing melanoma incidence (by more than 50 percent (1)) contained avobenzone but no photostabilizers. This means it is conceivable that modern day sunscreens with added photostabilizers may be even more effective in protecting against skin cancers than previously determined.
Back to topBoosting Compliance
Although popular media tends to focus on the type and percentage of UV filters and photostability, other product qualities such as fragrance, color, appearance, sensory profile, packaging, and cost are equally if not more critical.
Collectively, these are the features that determine the overall compliance — and hence efficacy. The best sunscreens are the ones preferred by consumers.
And yet the challenge in creating an aesthetically pleasant sunscreen is formidable. The majority of UV filters are made of oil-soluble molecules, and most recreational products have water-resistant polymers that prevent the filters from washing away with sweat or water. This combination of chemicals creates a tacky, greasy feel that can dissuade users from applying the product consistently or in sufficient volume.
To improve overall texture, manufacturers incorporate silicones, silicas, surfactants, and other chemicals that improve texture (slipping agents).
Back to topMaking the Whole Package Work
Modern-day sunscreens are expected to do more than merely prevent sunburns. They are recognized as a way to reduce skin cancers and slow skin aging. As advances in formulating sunscreens continue, consumers around the globe can expect to find products that offer protection to long-range UVA and short-range visible light.
These increasingly sophisticated products could potentially incorporate antioxidant and DNA repair enzymes that provide a host of other meaningful health benefits as well.
In spite of these advances, however, it’s imperative to emphasize to consumers that sunscreen is just one form of photoprotection and that avoiding excessive sun exposure, seeking shade, and wearing sun-protective clothing are ultimately more effective in reducing one’s level of exposure to UV light.
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