Education And Debate

Has the sun protection factor had its day?

BMJ 2000; 320 doi: https://doi.org/10.1136/bmj.320.7228.176 (Published 15 January 2000) Cite this as: BMJ 2000;320:176
  1. Brian Diffey (b.l.diffey@ncl.ac.uk), professor
  1. Regional Medical Physics Department, Newcastle General Hospital, Newcastle NE4 6BE
  • Accepted 15 October 1999

The concept of the sun protection factor was originally proposed by the Austrian scientist Franz Greiter and subsequently adopted by many regulatory authorities and the cosmetic and pharmaceutical industries. It is popularly interpreted as how much longer skin covered with sunscreen takes to burn compared with unprotected skin.1 This interpretation can encourage users to prolong their sun exposure accordingly, yet there is ample evidence that the numerical measure of protection indicated on the product pack is generally higher than achieved in practice.2 This mismatch between expectation and realisation may be one contributing factor to why use of sunscreens has been reported to be a risk factor in melanoma.3 I suggest that the role of sunscreens as a preventive measure against sunburn, and presumably skin cancer, would be strengthened if a qualitative rather than quantitative measure of photoprotection was used.

Summary points

If sunscreens were applied appropriately, to prevent sunburn there would be no need for sun protection factors higher than 15

People who use high factor sunscreens get sunburnt because of inadequate application

Numerical indicators of sun protection on sunscreen packaging can cause more confusion than clarity

Qualitative measures of labelling sunscreens are proposed that focus more on protection than on encouraging prolonged exposure to sunlight

What is the sun protection factor?

The sun protection factor is defined as the ratio of the least amount of ultraviolet energy required to produce a minimal erythema on skin protected by sunscreen to the amount of energy required to produce the same erythema on unprotected skin.4 Ten years ago most commercially available sunscreen products …

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