The Quest for Avobenzone Stabilizers and Sunscreen Photostability

Over the past 10 years, awareness of the detrimental effects of unprotected UV exposure has increased and, as a result, consumers are seeking higher levels of protection. Regulators and the industry have responded by requiring more stringent testing and providing more complete and balanced UV protection, respectively. In relation to testing, new regulations and guidelines were introduced in Europe, the US Food and Drug Administration (FDA) proposed a new monograph in 2007, and a globally harmonized standard is currently being developed by the International Organization for Standardization (ISO).

The most significant changes within these regulations are the new requirements for UVA protection and the added test for photostability of finished sunscreen formulations. The majority of sun care products currently require SPF levels of at least 30, reaching upwards of 50+. As a result, high levels of UVA protection are required in order to make a UVA claim, as well as to meet the guidelines. To confirm that UVA efficacy guidelines have been met, conform tests are available. In addition, the photostability of these materials must be demonstrated. Fulfilling these factors proves to be challenging in the EU, and is even more so if the FDA star-rating system is to be employed.

The objective of the present study was to establish photostability and UVA protection in several test sunscreen formulations. As will be shown here, butyl methoxydibenzoyl methane (BMDBM) exhibited the strongest and widest absorption curve of all the commercially available UVA filters tested. Thus, if properly stabilized, BMDBM could transfer its spectral performance benefits into higher levels of UVA protection. Since formulators seek robust UV filter combinations but are limited by cost, the authors explored several methods to photostabilize BMDBM. The performance of ten commercially available products that claim to stabilize BMDBM was investigated and their efficacy measured via two different test methods.

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