32 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS .' .,, "\ -' , i ,A' ... ?.•.' . '-,4: .... ' . • tz ,, ,•' ). ' •.', ' ',•...• .'• -.,-"- •' :'d, ,• -.. •'• •' , ',?• ,'It '":• - .•- •2 ' .•:•,,•' •,-,." .•' ,•¾ff•"•L -' i,'.,•Z•l• .•R_ ß •' '•)• ' ,• • . ': •"' Figure 8. SS-B treated. Elastic fiber (--) hyperplasia was even greater than with UVA alone. Many cells of the inflammatory repertoire were present and eosinophils (*) were abundant. Magnification X 7,800. Bar -- 2•m. regard to chronic effects of UV radiation, is as valid as a large body of evidence suggests (I9), molecules that absorb further into UVA I may be beneficial. Aside from physical blockers of UV radiation such as thick layers of zinc oxide, all sunscreens allow small amounts of radiation to reach the skin. Whereas erythema can be completely prevented, the cumulative "breakthrough" radiation may contribute to pho- toaging. We have shown that 1/2 of a UVA-I MED added to either V4 or 1A of a UVB MED produces dermal photodamage to hairless mice that is additive (20). Over a lifetime, these small amounts of UVA can add up to thousands of Joules of exposure with detrimental photoaging effects. The argument that SPF-I5 sunscreens provide adequate protection against erythema for most people and under most conditions is valid, but acute effects are not the only reason for requiring a sunscreen. Emphasis on acute effects fails to take into consideration the consequences of chronic exposure over a lifetime. ACKNOWLEDGMENTS The authors wish to acknowledge the invaluable participation of several associates: Marilyn J. Crosby and Sally Adams, animal treatment Kermit Wharton, animal care

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