Letters

Has the sun protection factor had its day?

BMJ 2000; 320 doi: https://doi.org/10.1136/bmj.320.7244.1274/a (Published 06 May 2000) Cite this as: BMJ 2000;320:1274

Information on sunscreens should warn against excessive sun exposure

  1. Philippe Autie, deputy director (philippe.autier{at}ieo.it),
  2. Gianluca Severi, biostatistician,
  3. Jean-François Doré, research director,
  4. Mathieu Boniol, research fellow
  1. Division of Epidemiology and Biostatistics, European Institute of Oncology, Milan 20141, Italy
  2. Institut National de la Santé et de la Recherche Médicale, Centre Léon Bérard, Lyons, France
  3. Department of Dermatology, Royal Liverpool University Hospital, Liverpool L7 8XP

    EDITOR—We approve of Diffey's proposition to clarify the information about sunscreens by abandoning numerical labelling and instead using measures focusing more on protection.1 In most fair skinned populations, sunscreens are used during recreational sun exposure, and quantities applied to the skin are only about one quarter of those used to measure the sun protection factor,2 even when sunscreens are given away free.3 It is unlikely that the quantity of sunscreen applied would increase substantially. Therefore, information on characteristics of sunscreen products should reflect the conditions in which most people will use them. Hence, ideally, the sun protection factor (or any other variable related to the properties of a sunscreen) should be measured using a thickness of sunscreen that agrees with actual use, for instance 0.5 mg/cm2.2

    Diffey looks at sunscreens only in terms of sunburn, assuming that more generous application would decrease the occurrence of sunburn. Skin cancer also needs to be considered because a higher sun protection factor is often assumed to confer greater protection against skin cancer. However, suberythemal doses of ultraviolet radiation may be involved in biological events relevant for cutaneous melanoma or basal cell skin cancer.

    A randomised trial in Australia showed that in cases of chronic exposure to the sun, daily use of sunscreen could decrease the incidence of both sunburn and squamous cell skin cancer (but not the incidence of basal cell skin cancer).4 5 The picture seems different in cases of recreational exposure to the sun, when the use of sunscreen does not seem to affect the occurrence of sunburn.2 3 A double blind randomised trial showed that use of higher sun protection factor sunscreens may relate to recreational sun exposure of longer duration.3 The longer exposure to the sun was unconscious—that is, the ability of sunscreens to delay sunburn supported people's intention to stay in the sun. These findings may partly explain why epidemiological studies found moderate increases in the risk of cutaneous melanoma and basal cell skin cancer associated with use of sunscreen. Where there is recreational exposure to the sun without control of time spent in the sun, increasing quantities of sunscreen applied to the skin could further encourage exposure to the sun. Information given to sunseekers should warn them that use of sunscreen could inadvertently increase the duration of their exposure to the sun, especially if they use a high sun protection factor sunscreen product.

    References

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    Sunscreen users need education in application technique

    1. Richard Azurdia, specialist registrar in dermatology,
    2. Lesley Rhodes, consultant dermatologist
    1. Division of Epidemiology and Biostatistics, European Institute of Oncology, Milan 20141, Italy
    2. Institut National de la Santé et de la Recherche Médicale, Centre Léon Bérard, Lyons, France
    3. Department of Dermatology, Royal Liverpool University Hospital, Liverpool L7 8XP

      EDITOR—Diffey's article describes many of the problems associated with sunscreen use.1 We have recently quantitatively assessed sunscreen application technique in photosensitive patients and shown that, even in this susceptible group, application is poor.2 The overall median sunscreen thickness was 0.5 mg/cm2, and key exposed sites such as the neck, temples, and ears were often missed completely. We showed that application technique can be improved by careful education, but even then the overall thickness of sunscreen rises to only 1 mg/cm2, which is half the standard thickness used in testing sun protection factors.3 An application thickness of 1 mg/cm2 is more appropriate for sunscreen testing; in addition, the public should be educated in appropriate sunscreen application methods.

      References

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      View Abstract

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