Sunscreen Controversies

Sunscreens are often applied carelessly and in insufficient amounts.

Although sunscreens are in common use and widely promoted, their use is less than ideal even in situations of high sunburn risk.¹ Two recent studies using fluorescent markers^2,3 confirm our suspicion that sunscreens are poorly applied. In both studies sunscreen was usually misapplied or incompletely applied, with the temples, ears and the back of the neck being most prone to neglect. Liberal amounts of sunscreen need to be applied systematically to avoid missing areas.^2,3 The fingertips should be used to cover areas with variable contours.² Squeezing the sunscreen onto the palms and rubbing the hands together before beginning application leaves much of the screen on the hands.² Gaughan and Padilla², and Azurdia, Pagliaro and Rhodes³ suggest that sunscreens containing fluorescent dyes could be an effective teaching tool leading to significant improvement in sunscreen application^2,3, in the same way that teeth staining tablets are used to show faults in brushing technique.²

UV protection given by clothing varies

Most people do not use sunscreens on the parts of their body covered by clothes, but are not aware that choice of fabrics and color of clothing affects the level of UV protection.¹ A plain white, single thickness, cotton T shirt has a Sun Protection Factor (SPF) of only seven⁴, two layers 19, green cotton 10 and dark blue denim 1700. Stretch and wetness reduce a fabrics ultra-violet protective factor⁵ (UPF) markedly. A recent article reviews these and other factors affecting the sun-protective qualities of textiles and suggests standards for sun-protective clothing.⁶ Wearing a hat with a wide brim provides a high degree of protection to the scalp and hair as well as the upper face.

Sunscreens and the elderly

The former concern that sunscreen use in the elderly might lead to vitamin D deficiency has been laid to rest to a certain extent⁷, but because of age related decrease in vitamin D production, some sun exposure for the elderly is probably to be recommended.⁸

Skin reactions to sunscreens

Although minor irritant reactions are common, allergic reactions are rare and the incidence of such reactions, even in photomedicine centers, is significantly overstated.^9–11

Sunscreens and photoaging

There is substantial evidence that high SPF sunscreens with broad spectrum protection can reduce the stigmata of photoaging.¹² Because UVA penetrates more deeply into the skin than UVB, a significant proportion of chronic photodamage may be secondary to UVA effects.¹²

Sunscreens and immunosuppression

Immunosuppression caused by ultraviolet light appears to be a significantly underappreciated phenomenon. There is growing evidence that such immunosuppression is of biologic significance.¹ Even suberythemal doses of UVB can induce immunosuppression.¹³

There is good evidence that appropriate broad spectrum sunscreens can prevent some aspects of photoaging and can prevent actinic keratosis and, perhaps by inference, squamous cell carcinoma. Sunscreens can prevent sunburn. There is no balance of evidence that would suggest that sunscreens directly prevent basal cell carcinoma or melanoma.¹
D.I. McLean and R. Gallagher¹

References

1. McLean DI, Gallagher R. Sunscreens: Use and misuse. Derm Clinics 1998; 16: 219–226.
2. Gaughan MD, Padilla RS. Use of a topical fluorescent dye to evaluate effectiveness of sunscreen application. Arch Dermatol 1998; 134: 515–517.
3. Azurdia RM, Pagliaro J, Rhodes LE. A new educational tool for improving sunscreen application technique. Brit J Derm 1998; 139:18.
4. Berne B, Fischer T. Protective effects of various types of clothes against UV radiation. Acta Derm Venereol (Stockh) 1974; 60: 459–460.
5. Australia/ New Zealand Standard, 4399:1996, Sun protective clothing: Evaluation and classification.
6. Adam J. Sun-protective clothing. J Cut Med Surg 1998; 3: 50–53.
7. Marks R, Foley PA, Jolley D, et al: The effect of regular sunscreen use on vitamin D levels in an Australian population. Arch Dermatol 1995; 131: 415-421.
8. MacLaughlin J. Holick MF: Aging decreases the capacity of human skin to produce vitamin D3. J Clin Invest 1995; 76: 1536-1538.
9. Foley P, Nixon R, Marks R, et al: The frequency of reactions to sunscreens: Results of a longitudinal population based study on the regular use of sunscreens in Australia. Brit J Dermatol 1993; 128: 512-518.
10. Szczurko C, Dompartin A, Michel M, et al: Photocontact allergy to oxybenzone: Ten years of experience. Photodermatol Photoimmunol Photomed 1994; 10: 144–147.
11. Trevisi P, Vincenzi C, Chieregato C, et al: Sunscreen sensitization: A three year study. Dermatology 1994; 189: 55-57, 1994.
12. Gilchrest BA: A review of skin ageing and its medical therapy. Brit J Dermatol 1996; 135: 867-875
13. Walker SI, Young AR. Sunscreens offer the same UVB protection factors for inflammation and immunosuppression in the mouse. J Invest Dermatol 1997; 108: 133–138.