The Making of An Effective Sunscreen

By Steven Q. Wang, MD,

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
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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).

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Photo 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.

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Boosting 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).

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Making 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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  1. Green, AC, et al., Reduced melanoma after regular sunscreen use: randomized trial follow-up. J Clin Oncol, 2011. 29(3): p. 257-63.

  2. Green, AC., et al., Daily sunscreen application and betacarotene supplementation in prevention of basal-cell and squamous-cell carcinomas of the skin: a randomised controlled trial. Lancet, 1999. 354(9180): p. 723-9.

  3. Wang, S.Q. and H.W. Lim, Current status of the sunscreen regulation in the United States: 2011 Food and Drug Administration’s final rule on labeling and effectiveness testing. J Am Acad Dermatol, 2011. 65(4): p. 863-9.

  4. Jones, C., Hollow sphere technology for sunscreen formulation, in Sun Protection, H. Ziolkowsky, Editor 2003, Verlag Fur chemische Industrie: Augsburg, Germany. p. 106-113.

  5. Bonda, C., The photostability of organic sunscreen actives: a review., in Sunscreens: regulations and Commercial Development. 3rd Ed., N. Shaath, Editor 2005, Taylor & Francis: Boca Rato. p. 321-349.