Debunking the Myths of Sunscreen

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Curtis Cole, PhD

Curtis Cole, PhD, from Johnson & Johnson Consumer Products, is a leading expert on sunscreens and has spent his life’s work on sunscreen technology and formulation. In this presentation, Dr Cole leads a discussion on what every dermatologist needs to know about the current status of sunscreens.

If sunscreens are so good for you, why is there so much noise about it?

Dr Cole mentions the fact that the press and media tend to comment on sunscreen use prior to sunscreen season(s). Many of these comments are read and misinterpreted by consumers and provoke questions around the safety of sunscreens. So what is the truth about sunscreens? Dr Cole states that fundamentally, ultraviolet radiation from sunlight is the major cause of skin cancer. Sunscreens can diminish the amount of ultraviolet radiation entering the skin; therefore, protecting and helping to prevent skin cancer.

Over the last ten years, several papers have been published demonstrating the proof that sunscreen does prevent and reduce skin cancer risk in humans if they are used on a regular basis. (Green A, et al. Lancet. 1999;354:723-729., Heather, L et al. Pigment Cell Melanoma Res. 2010;23:835-837., Adele C, et al. J Clin Oncol. 2011;29:257-263.)

What about estrogenicity and sunscreens?

The SCCNFP is a European “watchdog” group that oversees the safety of UV filters. In a 2001 meeting, the SCCNFP states that “it is of the opinion that the organic UV filters used in cosmetic sunscreen products, allowed in the EU market today, have no estrogenic effects that could potentially affect human health.” There really is no significant estrogenic effect from these UV filters. Studies have shown that estrogenic activity detected in in vitro binding assays did not correlate with in vivo activity. In addition, in vitro binding activity of UV filters are on the order of 1 to 3 million times less potent than estradiol, the standard estrogen compound. Research has also found that UV filters are several hundred times less potent than nutritional sources of estrogen, such as soy or natural supplements.

Does Retinyl Palmitate (RP) in sunscreens increase susceptibility to skin cancer?

The National Toxicology Program (NTP) conducted a nine-year study of RP in albino hairless mouse model. They utilized four concentrations of RP and two of Retinoic Acid and were evaluated against vehicle and untreated controls-solar simulator V source as well as BL and FS lamps. The endpoints were latency period to tumor appearance and tumor yield. Unfortunately this study was flawed; therefore, making the ability to draw a conclusion difficult if not impossible. The study was flawed for several reasons including:

  • Vehicle utilized 15% isopropyl adipate, a potent penetration enhancer
  • The top two concentrations of RP were toxic and had to be eliminated from the study
  • The “enhancing effect” of the vehicle over the untreated but irradiated mice was equivalent to 200% increase in the UV dose
  • The effect of RP was only evident in one gender of the mouse model and not the other

The results are contrary to human evidence that retinoids are chemoprotective to skin cancers. The NTP is considering redoing this study in order to achieve results that are more accurate.

Nano Materials in Cosmetic Materials

Nano materials are much more efficient in blocking UV and they are much more cosmetically acceptable. There are hundreds of papers that are published looking at the “nano sizes” questioning the penetration of TiO2 and ZnO particles. A recent paper by the FDA demonstrated that they could not find penetration from these nano-sized particles. A paper from Sayre R, et al. looked at whether “physical blockers” really act differently than “chemical” UV filters. They found that ZnO and TiO2 actually have a semiconductor energy band gap and absorb UV with the same mechanism as “chemical” UV filters. The “transparent” micronized inorganic filters have little scattering effect, if they did, they would be very visible on the skin. (Sayre R, Kollias N, Roberts R.  Physical sunscreens.  J. Soc. Cosmet Chem; 41:103-109)

What about inorganic (mineral filters)?

Are they better than organic (chemical) filter-based sunscreen? Dr Cole states that there is a much higher level of absorbance among the organic filters because the chemical filters are much more potent. Dr Cole is not saying that the physical filters are not useful, they do; however, have a place for patients who cannot tolerate the organic filters. Also of note, the organic filters are much more aesthetically pleasing.

Sunscreen

 

Do you really have to wait 15-20 minutes for sunscreen protection?

Sunscreen testing protocols mandate drying times of 15-20 minutes before SPF testing can begin; the mandatory labeling reflects this instruction. Actually, UV protection is instantaneous. However, it is important to remember that water resistance may require more drying time. All of the sunscreens that claim water resistance have a type of polymer that is set up to be a barrier against the water. Reapplication (every two hours) of sunscreen is another key component of preventing/reducing sunburns, in fact this is mandatory labeling by the FDA.  A paper in 2001 surveyed 57 people on a beach in Texas. Out of these subjects, there were at least 50 people who got sunburned on the beach; those who do not get sunburned re-applied their sunscreen every two hours. (1Wright M, Wright S, Wagner F.  Mechanisms of sunscreen failure.  J Amer Acad Dermatol. 2001;44:781-784)

Current Misconceptions on High SPF

Dr Cole asks the question of whether SPF 100 is really better than SPF 50. Here are the facts: SPF 100 blocks 99% of damaging UVR and SPF 50 blocks 98% of damaging UVR. Therefore, 1% of SPF 100 is getting through the filter and 2% of SPF 50 is getting through the filter. This means that it is the amount getting through the filter that matters. It’s not so much what you block, it is how much gets through. It would take twice as long to get the damage with SPF 100 than what you get with SPF 50.

Numerous studies have demonstrated that consumers typically under apply sunscreens. Higher SPFs can help compensate for under-application as SPF protection is directly proportional to the amount applied.

How does all of this information affect the products and labeling?
  • Most sunscreen products were unchanged
    • High SPF products (>SPF 50) still allowed
  • What did change?
    • All products now labeled with drug facts box
    • Test method for broad spectrum claims final – CW
      • Broad spectrum claims not allowed for products with SPF<15
  • Statement recognizing use of sunscreens for skin cancer prevention and skin aging is permitted (with an SPF of at least 15 and/or Broad Spectrum)
Broad Spectrum

Broad Spectrum is determined based on “critical wavelength” in vitro absorbance calculation, i.e., wavelength below which 90% of the absorbance is present. 370nm is the “pass/fail” critical wavelength for “Broad Spectrum Protection.” It is important to remember that critical wavelength measures the breadth of protection, yet it does not measure the magnitude; therefore, critical wavelength does not always correlate with UVA protection. The ability to achieve a critical wavelength of 370 becomes more and more difficult as SPFs increase above 30. Dr Cole recommends looking for products with an SPF:UVA-PF ratio of less than 3:1 (which is a requirement for European sunscreen products).

Individuals Particularly Sensitive

Patients/Consumers who are need of the best available protection are those who are highly sensitive (Phototypes I and II, photosensitive conditions and patients on immune suppressive drugs and those who have skin cancers. Others who are also in need of good protection are those who want to limit further photodamge, fine lines, wrinkling and pigmentation.

Why use a high SPF?

Extreme conditions of exposure warrant a higher SPF. These are conditions such as high altitude and those of high reflectivity such as ocean surface, sand and snow. In a controlled consumer trial (split-face, double-blind design) of 56 people at 8500 feet with all day sun exposure demonstrated that more individuals had sunburn using an SPF 50 versus an SPF 85 product. (Rigel et al. 2009. J Am Acad Dermatol;62, I:2:348-349)

Testing of high SPF products has been validated up to SPF 90. A controlled, randomized, multi-center trial was conducted using SPFs 16, 70 and 90 and four test laboratories using multiport and singleport solar stimulators. The results showed that all of the SPF levels could be distinguished from each other in the four labs; yet, no significant differences in SPF values of each product between laboratories. The testing demonstrated the ability of the laboratories to determine high SPF values with accuracy and reproducibility. (Stanfield,  Ou-Yang,  Chen, Cole, & Appa. 2011. Photodermatology, Photoimmunology & Photomedicine ;27:1,30-35)

Sunscreens and Squamous Cell Carcinoma and Malignant Melanoma

A randomized controlled study in Australia looked at sunscreen use (daily versus discretionary), risk of BCC and SCC (and melanoma). Use of an SPF 16 product and weight of the product brought in was measured every three months. The researchers found a significant reduction in the risk of SCC (RR 0.61; 95% CI 0.46 to 0.81). This suggests that melanoma may be preventable in adults with the regular use of sunscreen. (Green AC, et al. J Clin Oncol. 2011;29(3):257-263.)

Conclusions

Skin protection from damaging sunlight requires a multi-layer defense. Sunscreen should be part of the overall plan for protecting from sun damage. It is important to avoid unnecessary sunlight and you should avoid highest UVB intensities of sunlight (10am-4pm). Skin should be covered with clothing and a hat and high SPF should be used for skin that remains exposed.