Sun protection effectiveness

Gaynor Faye protecting her son Oliver from the sunThis page contains information about how sun protection can reduce the risk of skin cancer. Click on the links below to read about specific topics.

You can find out more about the evidence behind other health topics in our other  How do we know? pages.

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Covering up protects you from heavy sun exposure

Covering up with clothes, hats and sunglasses is a commonly recommended and effective way of protecting yourself from UV rays, second only to avoiding the sun altogether 1, 2. Measurements on over 5,000 fabrics showed that 97% of fabrics had an effective SPF greater than 10, and 85% had an SPF greater than 20.

Clothes tend to provide more protection if they 3:

  • are dark-coloured
  • are made of synthetic fabrics
  • are dry - if some fabrics are wet, their protection can be halved
  • have a close weave or are knitted.

Broad-rimmed hats and bucket hats provide the most UV protection for the whole face and head. Caps protect the nose and forehead but provide poor protection for other parts of the face 4, 5.

Too much UV exposure could also cause cataracts and melanomas in the uveal tract (the coloured part of the eye, which includes the iris) 6. Sunglasses should protect against these and wraparounds are recommended. Poorly-fitting glasses offer poor protection as sunlight can reflect off the back face of the lens back into the eye 7.

Sunglasses should state that they block out 100% of UVA and UVB rays. Alternatively, look for the ‘CE Mark’ and British Standard, or a UV 400 label. Remember that the UV-protective chemical on sunglasses is invisible, so the colour of the lens is not an indication of protection - in fact, the darkest sunglasses may cause pupil dilation and actually let more light in 8.

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SPF 15 sunscreen can help with sun protection

Many studies have shown that sunscreen can effectively protect us from harmful UV radiation 2. One trial found that people who used sunscreens have fewer moles, a risk factor for malignant melanomas 9.

Some researchers have failed to show that using sunscreens can lower the risk of melanoma. This is probably because many people use sunscreen to lengthen the time they spend in the sun, or to avoid using other protective measures like clothing 2, 12. Indeed, some studies have shown that people who use higher factor sunscreens spend more time in the sun 13 and have higher sunburn rates 14.

So sunscreens provide protection against UV radiation but must be used together with other protective measures, like seeking shade, covering up, or limiting exposure to the sun, if they are to be effective 2, 15.

The SPF or ‘factor’ of a sunscreen is a measure of the amount of sun protection it provides. Experts have found that in Europe, SPF 15 sunscreen is appropriate for protection even from midday summer sunshine 2, 16. Sunscreens with SPF values higher than 30 offer little additional protection for a lot more money.

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Sunscreen must be used properly to provide protection

Sunscreen should be applied evenly, thickly and regularly to be effective. SPF measurements are based on the assumption that people apply 2mg/cm2 of sunscreen on their body 2. But studies have found that people only apply 0.5-1mg/cm2 17. So most people get only a quarter to a half of the protection they should be getting 18.

And people often miss out heavily exposed bits like the ears and parts of the neck 16. Like painting a textured wall, two coats are usually needed because the first coat won’t evenly cover the entire surface.

Sunscreens should be reapplied regularly, especially after any activity that could remove it such as sweating, swimming, towelling or lying on sand. An Australian study found that re-application increases total sun protection by 2-3 times compared to a single application 19. And another study found that reapplying sunscreen 20 minutes after going outside provided up to 85% more protection that reapplying after 2 hours 20.

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References

  1.  Saraiya, M., et al., Interventions to prevent skin cancer by reducing exposure to ultraviolet radiation: a systematic review. Am J Prev Med, 2004. 27: p. 422-66. PubMed
  2.  IARC, Sunscreens. IARC Handbooks of Cancer Prevention. Vol. 5. 2001, Lyon: IARCPress. Link
  3.  NPRB, et al., Protection from UVR by Clothing. 1998. Link
  4.  Diffey, B.L. and J. Cheeseman, Sun protection with hats. Br J Dermatol, 1992. 127(1): p. 10-2. PubMed
  5.  Davis, S., et al., Clothing as protection from ultraviolet radiation: which fabric is most effective? Int J Dermatol, 1997. 36(5): p. 374-9. PubMed
  6.  Vajdic, C., et al., Sun exposure predicts risk of ocular melanoma in Australia. Int J Cancer, 2002. 101: p. 175-82. PubMed
  7.  Sakamoto, Y., M. Kojima, and K. Sasaki, [Effectiveness of eyeglasses for protection against ultraviolet rays]. Nippon Ganka Gakkai Zasshi, 1999. 103(5): p. 379-85. PubMed
  8.  Pion, I., Educating children and parents about sun protection. Dermatol Nurs, 1996. 8: p. 29-36. PubMed
  9.  Gallagher, R., et al., Broad-spectrum sunscreen use and the development of new nevi in white children: A randomized controlled trial. JAMA, 2000. 283: p. 2955-60. PubMed
  10.  Diffey, B.L. and J. Grice, The influence of sunscreen type on photoprotection. Br J Dermatol, 1997. 137(1): p. 103-5. PubMed
  11.  Stokes, R. and B. Diffey, How well are sunscreen users protected? Photodermatol Photoimmunol Photomed, 1997. 13: p. 186-8. PubMed
  12.  Weinstock, M., Do sunscreens increase or decrease melanoma risk: an epidemiologic evaluation. J Investig Dermatol Symp Proc, 1999. 4: p. 97-100. PubMed
  13.  Autier, P., et al., Sunscreen use and duration of sun exposure: a double-blind, randomized trial. J Natl Cancer Inst, 1999. 91: p. 1304-9. PubMed
  14.  Diffey, B., Sunscreen isn't enough. J Photochem Photobiol B, 2001. 64: p. 105-8. PubMed
  15.  National Radiological Protection Board, Heatlh effects from ultraviolet radiation: report of an advisory group on non-iodising radiation. Documents of the NRPB. Vol. 13. 2002. Link
  16.  Diffey, B., Has the sun protection factor had its day? BMJ, 2000. 320: p. 176-7. PubMed
  17.  Stenberg, C. and O. Larko, Sunscreen application and its importance for the sun protection factor. Arch Dermatol, 1985. 121: p. 1400-2. PubMed
  18.  Azurdia, R., et al., Sunscreen application by photosensitive patients is inadequate for protection. Br J Dermatol, 1999. 140: p. 255-8. PubMed
  19.  Prium, B., L. Wright, and A. Green, Do people who apply sunscreens, reapply them? Australas J Dermatol, 1999. 40(2): p. 79-82. PubMed
  20.  Diffey, B., When should sunscreen be reapplied? J Am Acad Dermatol, 2001. 45: p. 882-5. PubMed