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Clin Exp Dermatol. 2012 Dec;37(8):904-8. doi: 10.1111/j.1365-2230.2012.04388.x. Epub 2012 Oct 10.

Relationship between sun-protection factor and application thickness in high-performance sunscreen: double application of sunscreen is recommended.

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  • 1Research Laboratories, KOSÉ Corporation, Tokyo, Japan.



High-performance sunscreen protects both healthy consumers and photosensitive patients from strong ultraviolet (UV) exposure. The sun-protection factor (SPF), which indicates the efficacy of UV protection, is determined using a prescribed sunscreen application thickness of 2.0 mg/cm(2). Therefore, users should apply at least 2.0 mg/cm(2) of sunscreen to obtain the level of UV protection expected from a product. In most cases, however, users apply insufficient amounts of sunscreen.


To determine the amount of sunscreen applied under specific conditions, and the relationship between application thickness and SPF value in high-performance sunscreen.


The amount of applied sunscreen was calculated under practical conditions and conditions that directed a double application. The SPF values of high-performance sunscreen applied at three thicknesses (2.0, 1.0 and 0.5 mg/cm(2)) were determined according to the international SPF testing method. RESULTS. The relationship between SPF value and application thickness correlated in a logarithmic curve. The mean application thickness under practical conditions was approximately 1 mg/cm(2), and directing subjects to use a double application increased the application thickness to nearly 2 mg/cm(2).


Encouraging a double application of sunscreen will help users apply products at a thickness sufficient to achieve expected SPF efficacy. We recommend that guidance on double application of sunscreen should be posted in public locations where sunscreen is likely to be in use.

[PubMed - indexed for MEDLINE]
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