L'Oreal Critical Wavelength Criticism Disputed By P&G

L'Oreal used a "flawed technical analysis" in assessing the critical wavelength method as a UVA sunscreen testing assay, Procter & Gamble asserts in May 2 comments to FDA.

P&G disputes L'Oreal's March 3 correspondence to the agency, which "distorted" use of the critical wavelength method and falsely represented the in vitro assay as "inadequate," the company maintains.

"There continues to be a misrepresentation of the critical wavelength based on a flawed technical evaluation, which evidently serves as the basis" for promoting an alternative in vivo test such as Persistent Pigment Darkening, P&G claims. PPD was developed by L'Oreal's R&D team.

In its comments to FDA, L'Oreal argued the critical wavelength method, or "modified Diffey," fails to provide an adequate measure of UVA efficacy. The company submitted similar comments to FDA in 1998.

P&G counters, however, that L'Oreal's use of an in vitro protection factor for UVA-induced erythema as a "benchmark" for analysis is "entirely inappropriate." The UVAePF, which is weighted for shorter UV wavelengths, "does not properly evaluate efficacy" for longer UVA wavelengths, the firm says.

In addition, the comments continue, UVAePF is measured using the absolute height of the absorbency curve, "an approach that is known to generate inaccurate protection factors." Therefore, P&G concludes, the use of UVAePF as a benchmark for the critical wavelength is "patently unsuit[able]."

P&G has "numerous concerns," about PPD. While the critical wavelength complements the SPF method, PPD and other available in vivo methods are "redundant with SPF" and yield "limited information regarding long-wave UV protection of sunscreen products," the firm asserts.

The combination of the critical wavelength and SPF, on the other hand, offers a "complete description of a product's inherent photoprotective characteristics," P&G maintains.

In its earlier comments, L'Oreal maintained PPD is "sensitive and specific to all UVA wavelengths and equally sensitive to the variety of UVA filtration schemes tested."

In vivo UVA tests in general present technical problems, P&G contends. First, results are communicated on an exponential scale and "give consumers a false impression of [the] magnitude of absorption differences."

"The outcome of any in vivo UVA test is the generation of a 'protection factor,' a misleading number since there are presently no biological surrogates for any long-term damage attributed to long-wave UV," the company says.

For example, two sunscreens with protection factors of five and 10, respectively, would suggest the first product is half as effective as the second, although "the real difference is quite small," P&G notes.

Furthermore, PFAs do not account for real-life UV light, which is affected by altitude, cloud cover and other environmental factors. Such tests also are dependent on dose amounts and application thickness, the firm states. The critical wavelength, however, is the "same regardless of the dose or amount of product applied."

As a result, P&G argues, "it is difficult to understand how the advancement of any current in vivo method to evaluate long-wave UVA protection is being done for altruistic reasons or to otherwise benefit consumers." L'Oreal is developing an in vitro method to validate PPD.

P&G's comments are the latest in a series of arguments with L'Oreal on UVA testing. Procter argued against the use of an in vivo assay like PPD in comparing a UVA test with SPF in November 1998 (¹ (Also see "Critical Wavelength Method Should Face In Vitro Comparator, P&G Says" - Pink Sheet, 30 Nov, 1998.)).

P&G does not market a traditional sunscreen product in the U.S., although the firm sells Olay Complete UV Protection Moisturizer with micronized zinc oxide.

The appropriate method to designate the level of UVA protection in sunscreens is an ongoing topic of debate between FDA and industry; the American Academy of Dermatology hosted a UVA consensus conference in February to encourage public discussion on the issue (² (Also see "In Vivo UVA Sunscreen Tests "Clinically Irrelevant...Unethical" - Diffey" - Pink Sheet, 14 Feb, 2000.)).

FDA extended the implementation date for the OTC sunscreen final monograph to Dec. 31, 2002 from May 21, 2001 to provide time to resolve outstanding UVA and UVB testing issues (³ (Also see "FDA Extends Sunscreen Monograph Implementation Date To December 2002" - Pink Sheet, 11 Oct, 1999.)).