Sunscreen Research: Which sunscreens work best in research studies?

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Evaluation of the capacity of sunscreens to photoprotect lupus erythematosus patients

Suncreen A (UVB: Octocrylene; UVA: Mexoryl SX, Mexoryl XL, Parsol 1789; TiO2) was by far the most effective by protecting in 11/11 patients. This protective capacity was corroborated by studies in which strong ICAM-1 mRNA expression was found in unprotected test areas, but not in sunscreen A pretreated sites. In contrast to sunscreen A, sunscreen B (UVB: Eusolex 6300, Parsol MCX, Uvinul T150, Neohelipan; UVA: Parsol 1789; TiO2) protected in 5 patients and sunscreen C (Eusolex 6300, Parsol MCX, Uvinul T150; UVA: Parsol 1789; TiO2) in 3 out of 11 patients. [ Evaluation of the capacity of sunscreens to photoprotect lupus erythematosus patients Stege]

Shining Light on UVA Importance
Source: Dermatology Times
By: Jennifer Clark
Originally published: March 1, 2003


Sunscreen containing UVA filter Mexoryl XL (upper part of the arm) provide significant protection against the induction of skin lesions in PLE patients. (Photograph courtesy of André Rougier, Ph.D.)
Asnières, France - The amount of ultraviolet A radiation (UVA) filtering is as important as labeled sun protection factor (SPF) levels in determining the effectiveness of sunscreens, according to AndrÒougier, Ph.D. However the UVA blocker he prefers most, Mexoryl, remains unavailable in the United States as it awaits FDA approval.

"Much photodamage is produced by UVA rather than UVB. A good SPF is not enough. To be well protected you need a high SPF and a high UVA protecting factor at the same time. Moreover, the filtering system must be photostable, which is the case of only a few sunscreen products on the U.S. market," said Dr. Rougier, who is scientific director for La Roche-Posay Pharmaceutical Laboratories, Asnies, France, which is owned by L'Or,.

"In the States most of the products have deficient UVA filtering capacities," he continued. "The over-the-counter products are not sufficient compared with Europe and Asia in terms of UVA. In terms of UVB protection, it's OK. Mexoryl SX and Mexoryl XL [both patented by L'Or,] are two UVA filters that are used all over the world, but not in the States, and that is the best UVA protection. These filters have been approved in Europe, respectively, in 1992 and 1999, and in Japan in 1999 and 2002. Sunscreens containing these filters are available in Europe, Asia, Latin and South America. Millions of units have already been sold without any adverse effects."

Dr. Rougier and colleagues studied 20 women volunteers, average age 30, who were exposed to simulated UV radiation using a broad-spectrum UV lamp to induce photodermatosis. Each volunteer first applied sunscreens with SPF 60, but the topical agents varied in UVA protection measuring from 4 to 28, according to the persistent pigment darkening method (PPD). PPD is frequently used to measure UVA protection because its action spectrum extends across the UVA and is a biological end point rather than in vitro. Dermatologists observed each volunteer for the presence of polymorphous light eruption. Products with poor UVA protection also resulted in more significant skin damage.

Corroborating Research Professor Jean Krutmann and his research team at Heinrich-Heine University, Dusseldorf, Germany, also apparently support the use of Mexoryl as UVA protection agents. They followed 11 patients with photosensitive lupus erythematosus (LE). Each patient served as his or her own control, applying all three commercially available sunscreens in a double-blind comparative study. Using a standard phototest with a combination of UVA and UVB radiation, all patients developed LE-specific skin lesions. But the sunscreen with Mexoryl SX, Mexoryl XL, parsol 1789 and Ti02 to target against UVA rays "was by far the most effective in protecting 11of 11 patients." The other two sunscreens included parsol 1789 and Ti02 alone, protecting five patients with the second formulation and only three patients with the third formulation. The results were verified by strong ICAM-1 mRNA expression in unprotected test areas. The researchers concluded, "The use of sunscreens is beneficial to LE patients. Effective protection, however, might vary considerably between different sunscreens."


Dr. Rougier
A Canadian study shows SPF fails to provide enough information about how well sunscreens protect against UVA rays. University of Montreal, Quebec, researchers compared six sunscreens with SPF of 21 or more using the persistent pigmentation darkening method. After two hours, they found significant difference in UV radiation-induced pigmentation, confirmed by colorimetric and visual assessments. They concluded, "The labeled sun protection factor of the tested sunscreens was not predictive of the UVA protection level."

Studies by other investigators at the L'Oreal Research Center, Clichy, France, recommend people use daily protection against the sun. Twelve healthy volunteers were exposed five days a week to simulated solar radiation. The exposure time included one minimal erythema dose. They treated part of their skin with a daily use cream, containing UVA and UVB absorbers, including uvinul N539, parsol 1789, and Mexoryl SX.

After six weeks, the untreated skin showed signs of several biological changes, while the cream appeared to prevent them. The untreated skin had significant increases in stratum corneum and stratum granulosum thickness, increased tenascin expression but decreased type 1 procollagen in the dermis, as well as melanization and changes in skin hydration and microtopography.

Catching Up "When they prescribe sunscreens to patients, dermatologists should be aware both of the SPF and UVA protection ... that is the main issue," said Dr. Rougier. "Americans are probably the worst who are not protected from the sun and particularly from UVA radiations."

Sun exposure is well documented to cause skin photoaging and eventually, various forms of cancer. "The aim of sunscreens is not to increase sun exposures, but to decrease risks of reasonable exposures. Even well protected, sun is dangerous, Dr. Rougier said.

La Roche-Posay and LOréal funded Dr. Rougier's research.

http://www.dermatologytimes.com/dermatologytimes/article/articleDetail.jsp?id=50923  

Prevention of Polymorphous Light Eruption and Solar Urticaria
R. Bissonnette, MSc, MD, FRCPC
Division of Dermatology, University of Montreal Hospital Centre, Montreal, Quebec, Canada
Skin Therapy Letter • Editor: Dr. Stuart Maddin • Vol. 7 No. 7 • September 2002

http://www.skintherapyletter.com/download/stl_7_7.pdf 

 In this study the two sunscreens that afforded the highest UVA protection contained Parsol®1789, which has a maximal absorption at 358nm. Anthelios®L also contained Mexoryl SX for UVA protection, which has a maximal absorption at 345nm. The sunscreens compared were: Anthelios®L 60, Bain de Soleil®25, Coppertone®45, Hawaiian Tropic®50, Presun®21 and Presun®30. In order of decreasing efficacy the best sunscreens for UVA protection were Anthelios®
L,Presun®30, PreSun®21, Bain de Soleil®25, Coppertone®45and Hawaian Tropic®50.The two sunscreenscontaining physical agents only (i.e., PreSun®21 and Bain deSoleil®25) were not as efficient for UVA protection, which
could be related to the fact that the spectral protection of micronized titanium dioxide (TiO2) decreases with increasing
UVAwavelength. This study confirmed that SPF, a measure of UVB protection, is not indicative of UVA protection
provided by sunscreens. It also illustrates how difficult it is to select a sunscreen with broadspectrum and high UVA
protection, since SPF is the only indicator of UV protectionon sunscreen labels in North America. 

Broad-spectrum photoprotection: the roles of tinted auto windows, sunscreens and browning agents in the diagnosis and treatment of photosensitivity. Johnson JA, Fusaro RM.

Dermatology. 1992;185(4):237-4, Johnson JA, Fusaro RM.
Department of Internal Medicine/Dermatology, University of Nebraska Medical Center, Omaha 68198-4360.

Since window glass absorbs sunlight below 320 nm, it provides a means of assessing sensitivity to longer wavelengths, i.e. UVA and visible radiation. Positive responses to the query of whether symptoms develop in the auto with the windows up must now be interpreted with regard to the possible presence of tinted plastic film on side and rear windows. These films block nearly all UVA radiation, as does the plastic interleaf of windshields. Thus, occupants of an auto equipped with plastic film receive photoprotection from UVB radiation and well into the UVA region. We define three classes of topical sunscreens: (1) conventional UVB screens, (2) broad-spectrum preparations containing a UVB screen and a UVA absorber and (3) browning agents such as dihydroxyacetone (DHA) that produce a skin coloration that absorbs in the low end of the visible region, with overlap into long-wavelength UVA. By considering responses of photosensitive persons in autos with tinted or untinted windows, coupled with efficacy of appropriate sunscreens, we produced an algorithm defining three photosensitivity subsets. Persons sensitive to long-wavelength UVA and/or visible radiation will benefit from tinted auto windows. In particular, patients with lupus erythematosus (LE) have actively promoted legislation allowing tinted windows. Support for their position is documented by recent reports of induction of lesions in LE patients by exposure to UVA and visible radiation. The brown color produced by DHA is a useful adjunct to the screening action of broad-spectrum sunscreens. Development of a durable color overnight allows application of the DHA preparation in the evening, thus eliminating possible interference with sunscreen use during the day.

PMID: 1477415 [PubMed - indexed for MEDLINE]

Evaluation of the capacity of sunscreens to photoprotect lupus erythematosus patients by employing the photoprovocation test.Stege

Photodermatol Photoimmunol Photomed. 2000 Dec;16(6):256-9. , Stege H, Budde MA, Grether-Beck S, Krutmann J.
Department of Dermatology, Heinrich-Heine University Dusseldorf, Germany.

Although sunscreens are widely used to photoprotect patients with photosensitive lupus erythematosus (LE), standardized controlled studies that can prove their efficacy for this indication have been lacking. Therefore, in the present study, the capacity of three different, commercially available sunscreens to prevent the development of skin lesions that have been induced in LE patients under standardized, reproducible conditions by employing a provocative phototest was assessed. In a double blind, intraindividual comparative study, 11 patients with LE were photoprovoked according to a standard protocol. All patients developed LE-specific skin lesions upon photoprovocation with a combination of UVA plus UVB radiation. Each of the sunscreens tested prevented the development of skin lesions in this assay, but to various extents. Suncreen A (UVB: Octocrylene; UVA: Mexoryl SX, Mexoryl XL, Parsol 1789; TiO2) was by far the most effective by protecting in 11/11 patients. This protective capacity was corroborated by studies in which strong ICAM-1 mRNA expression was found in unprotected test areas, but not in sunscreen A pretreated sites. In contrast to sunscreen A, sunscreen B (UVB: Eusolex 6300, Parsol MCX, Uvinul T150, Neohelipan; UVA: Parsol 1789; TiO2) protected in 5 patients and sunscreen C (Eusolex 6300, Parsol MCX, Uvinul T150; UVA: Parsol 1789; TiO2) in 3 out of 11 patients. These studies indicate that the use of sunscreens is beneficial to LE patients because it can prevent the development of UV radiation-induced skin lesions. Effective protection, however, might vary considerably between different sunscreens.

PMID: 11132128 [PubMed - indexed for MEDLINE]

CONTACT: Dominique Moyal
L[:apos:]Oréal 8/12 Impasse Barbier Clichy, France 92117

UVA photoprotection:clinical aspect

ABSTRACT:
Experimental findings show that UVA radiation can cause damages in human skin such as: genetic damage in cellular DNA, photoimmunosuppression, photoaging and photodermatosis like Polymorphous Light Eruption (PLE). Increasing concern about these effects has led to the developmentof sunscreens which effectively attenuate the UVA radiation reaching the skin. Sunscreens efficacy is currently evaluated by the sun protection factor (SPF)method using sunburn as endpoint.The action spectrum for sunburn is heavily weighted in the UVB range with a small contribution from the UVA. Due to the fact that UVA protection level can not be effectively assessed by the SPF, we have used the Persistent Pigment Darkening (PPD)method to select sunscreen products to study their efficacy in the prevention of PLE and photoimmunosuppression. We have shown a direct relationship between the PLE prevention and the PPD UVA-PF of the products. Maximal prevention was achieved by sunscreen providing a high protection throughout the entire UV spectrum and in particular in the UVA one. The efficacy of two products with a same SPF15 but with different UVA-PF (10.4 and 2.4)against the UV-induced immune suppression was compared using the delayed type hypersensitivity (DTH) reaction to recall antigens. They were found significantly different. Prevention of UV-immune suppression was achieved with the sunscreen having the higher UVA-PF, conversely a decrease of DTH reaction was observed after UV exposure with the lower UVA-PF suncreen. The UVA-PF assessed by the PPD method affords an important information in addition to the SPF value. Consequently we propose to complete the labelling of sunscreen products by using the SPF/UVA-PF ratio.

DOCUMENT LISTING FOR

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Photodermatol Photoimmunol Photomed. 1997 Oct-Dec;13(5-6):186-8.Related Articles, Links

How well are sunscreen users protected?

Stokes R, Diffey B.

Regional Medical Physics Department, Dryburn Hospital, Durham, UK.

Previous studies have shown that people often apply less sunscreen than the recommended amount of 2 mg/cm2. Our purpose in this study was to determine objectively how photoprotection varies with application thickness. The protection provided by differing quantities of sunscreens containing varying amounts of titanium dioxide was measured in vitro using excised human epidermis as the substrate. It was found that application thickness had a significant effect on the sun protection factor (SPF), with most users probably achieving a mean SPF of between 20-50% of that expected from the product label. Underprotection due to inadequate application, coupled with overexposure to the sun, might partially explain why sunscreen use has been reported to be a risk factor in melanoma.

PMID: 9542755 [PubMed - indexed for MEDLINE]

Entrez PubMed

Sunscreen application by photosensitive patients is inadequate for protection.
Azurdia RM, Pagliaro JA, Diffey BL, Rhodes LE., Br J Dermatol. 1999 Feb;140(2):255-8. 
Photobiology Unit, Department of Dermatology, Royal Liverpool University Hospital, Liverpool L7 8XP, U.K.

Photosensitive patients often comment that sunscreen products seem of little benefit. We used fluorescence spectroscopy to assess quantitatively their sunscreen application technique. A dose-response relationship for sunscreen skin surface thickness and fluorescence intensity was determined for an intrinsically fluorescent sunscreen, Neutrogena sun protection factor (SPF) 15. Ten women with long-standing photosensitivity conditions were asked to apply this sunscreen in the manner they would normally on a bright sunny day. Fluorescence measurements were taken from all unclothed body areas, comprising 17 sites of the head, neck, upper and lower limbs. Geometric regression analysis of the dose-response data showed a high level of correlation (r = 0.99) between sunscreen thickness and fluorescence intensity, allowing fluorescence measurements to be converted to an equivalent sunscreen thickness. The overall median sunscreen thickness was 0.5 mg/cm2, with median thicknesses of individual sites ranging from 0 to 1.2 mg/cm2. The most frequently missed sites were the posterior neck, lateral neck, temples and ears, all of which had median thicknesses of 0 mg/cm2. Hence, photosensitive patients fail to apply sunscreen in some prominently exposed sites, and use average thicknesses far less than the manufacturers' recommendation (2 mg/cm2). The level of protection is much lower than anticipated from the stated SPF of the product.

PMID: 10233218 PubMed