Zinc Oxide or Avobenzone boosts sunscreen protection

Written by on March 15, 2006 in Sunscreens for Rosacea Sufferers with 0 Comments

This paper shows that adding zinc oxide or Avobenzone to a sunscreen improves the broad spectrum protection that it offers – as much as double or triple their UVA protection. Zinc Oxide and Avobenzone are the only 2 approved sunscreens for broad spectrum protection.

Avobenzone and zinc oxide: Maximizing UVA efficacy for effective broadspectrum protection in sunscreen products

Exposure of unprotected skin to solar UV radiation (SUVR) induces damage that can lead to the clinical appearance of erythema or edema from acute exposure and photoaging or cancer from chronic exposure. Solar UVR comprises UVB (290-320 nm) and UVA (320-400 nm) wavelengths, with the latter accounting for about 94% of the solar UVR striking earth’s surface. UVR damages molecules in skin either directly after absorption or indirectly through oxidative events mediated by reactive oxygen species (ROS). UVB primarily exerts direct damage (especially to DNA), whereas UVA operates mainly through the intermediacy of ROS.

Topical application of sunscreens affords skin significant protection during periods of exposure to SUVR. While specifically designed to protect against erythema, sunscreens also help protect against immune suppression, photoaging, and cancer. Initially, sunscreen products focused more on protecting skin from the UVB portion of SUVR, since the shorter wavelengths are more potent biologically.

However, accumulating experimental evidence has suggested that SUVR evokes much more complex biologic responses within skin than can be explained by merely adding responses caused by UVB to those caused by UVA separately. This suggests that UVA plays an important role in orchestrating skin damage caused by SUVR and provides compelling reasons for sunscreen products to protect skin broadly from both UVB and UVA in a balanced manner.

Here, we present SPF and PFA (protection factor A) measurements to demonstrate the power of either avobenzone or zinc oxide (ZnO) in combination with other sunscreens to deliver high SPF broad-spectrum protection to human skin.

We show that some sunscreen combinations with avobenzone or ZnO can double or triple the UVA protection, compared with compositions of similar SPF that do not contain avobenzone or ZnO. Avobenzone and ZnO currently represent the only sunscreen actives approved for use in the United States that are capable of conferring true broad-spectrum protection.

We also demonstrate that the addition of recognized photostabilizers and omission of photochemically incompatible ingredients also preserve avobenzone’s photostability after exposure up to 15 MED. Enhancing avobenzone’s photostability enables it to provide sustained UVA and significant protection during prolonged periods of exposure to SUVR.

Author disclosure: Nothing disclosed at press time.

Supported by Schering-Plough Consumer HealthCare Products. (maker of the coppertone and bain de soliel brands)

Poster Discussion Session P2604, American Academy of Dermatology, 64th Annual Meeting, March 3-7 2006, San Francisco. Supplement to Journal of The American Academy of Dermatology, March 2006, Volume 54, Number 3.

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About the Author: David Pascoe started the Rosacea Support Group in October 1998. .

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