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Features Departments Information |
 Robin L. Hornung, MD, MPH
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Dermatology quiz ROBIN L. HORNUNG, MD, MPH aSpring 1998 A SEVEN-MONTH-OLD Caucasian infant presented to the dermatology clinic with a bright red rash over his central face. He had a history of atopic dermatitis but was otherwise healthy. His family history was notable only for his mother's remote history of a seronegative arthritis.  FIGURE 1. Bright red erythematous patches involving the cheeks and nose, sparing the forehead and scalp. On physical examination, the infant was active and alert, although slightly irritable. His facial skin was notable for bright red erythematous patches coalescing over his cheeks and nose Figure 1. He also had some areas of fine desquamation on his cheeks where there had been some blistering. His scalp and forehead were spared. The most likely diagnosis is:
A. Neonatal lupus
Answer: C. A sunburn reaction Upon further questioning, the parents reported that the rash began the evening before after the family had gone for a long afternoon hike during a partially cloudy, cool spring day. They had placed a hat on the infant's head, but decided they did not need any sunscreen given it was cloudy and the hike did not take place in the midday sun. What would have been the best sunscreen for this child?:
A. A gel-based preparation with SPF 30
Answer: E. A physical sunscreen with titanium dioxide A sunburn reaction is the most conspicuous acute cutaneous response to ultraviolet (UV) radiation, and it is manifested by an inflammatory erythema. Erythema is a result of increased blood flow in the superficial and deep dermal vascular plexuses, and it can be associated with other classical signs of inflammation such as pain, edema, and pruritus. 1 An individual's skin pigmentation affects the amount of UV radiation needed to induce the sunburn response, with highly pigmented or dark colored skin being the most protected. The wavelength of UV light is another important determinant in the sunburn reaction. Although UVB (290 to 320 nanometers) is much more erythemogenic, the large quantity of UVA (320 to 400 nm) in terrestrial sunlight can contribute as much as 15 percent of the erythemal effectiveness at the solar zenith.2 The erythema that is produced after UVB overexposure is delayed in onset and usually appears 3 to 5 hours later, reaching a maximum intensity between 12 and 24 hours.3 The erythema caused by UVA tends to peak anywhere between 6 and 24 hours. The UV spectrum also includes UVC (200 to 290 nanometers), but this high energy radiation cannot reach the earth's surface as it is screened out by the stratospheric ozone layer, a protective gaseous shield that envelops the planet. Treatment of the inflammatory sunburn reaction is best if it is prevented through photoprotection! This is especially important in light of the recent skin cancer epidemic and the link between childhood sunburns and the risk of developing malignant melanoma. Given that 80% of lifetime sun exposure occurs before the age of 18, it is clear that photoprotective habits must be learned and practiced at a very young age.4 Recently, the American Academy of Dermatology (AAD) and the Centers for Disease Control and Prevention (CDC) developed photoprotection recommendations as part of their National Skin Cancer Agenda.5 These recommendations can be found in Table 1. A major component to achieving photoprotection is through the use of sunscreens. Sunscreens are preparations which protect the skin from UV radiation either through absorbing light (i.e., the chemical sunscreens) or by reflecting and scattering light (i.e., the physical sunscreens). Sunscreens were originally designed to protect against sunburn, enable longer sun exposure, and promote tanning. However, sunscreens are now promoted as a method for preventing sunburn, skin cancer, and skin aging ("photodamage"). There are several factors to consider when selecting a sunscreen. These include UVB protection, UVA protection, substantivity, and the allergic potential. Ultraviolet-B protection is the most widely recognized component of sunscreens and is represented by the Sun Protection Factor (SPF). This number is a laboratory-derived measure of sunscreen protectiveness and is the ratio between the dose of UV light required to produce minimal erythema on sunscreen-protected skin and the dose required to produce it on unprotected skin. The higher the number, the more protection afforded, although this is not a linear relationship. A SPF of 15 is the minimum recommended for lightly pigmented skin. UVA protection is now offered in most sunscreens, but unfortunately the labels usually provide no indication of the level or wavelengths of UVA protection. Most UVA protecting sunscreen agents only offer protection against short wave UVA. The physical sunscreens (e.g., those containing titanium dioxide or zinc oxide) tend to protect over a broader wavelength range and are highly recommended for children. Another aspect in determining sunscreen efficacy is its substantivity. Substantivity refers to whether a sunscreen is waterproof, water resistant, or sweat resistant. A waterproof sunscreen maintains its photoprotective capability after 80 minutes of active water immersion, compared to 40 minutes from a water resistant sunscreen.6 A sweat-resistant sunscreen is one that can protect the skin after 30 minutes of uninterrupted heavy perspiration. Based on these qualities, sunscreen products should be reapplied at appropriate intervals after swimming or sweating (keeping in mind that reapplication does not increase the SPF in an additive way). Allergic reactions to sunscreens are relatively uncommon, with studies showing the frequency between 0.1% to 2% in the patient population.7 Many major chemical sunscreen categories have been implicated, including PABA, glyceryl PABA, and padimate O. The physical sunscreens are not cutaneous sensitizers and therefore are tolerated better in people with hypersensitive skin. Most sunscreen reactions reported are of the irritant type from the sunscreen vehicle itself. The alcohol-based gels, liquids, or sprays tend to be the most irritating, and therefore should be avoided on sensitive skin, especially in children. Unfortunately, photoprotection is not always practiced, and sunburns often result. As in this case, people often mistakenly believe the myth that cloud cover can protect against UV radiation exposure. In addition to the cloud effect, it is important to know that 80% of incident UV light can be scattered or reflected from snow, sand, concrete, water, and metallic surfaces.8
If a sunburn does occur, several palliative measures are available depending upon its severity. Oral fluids should always be encouraged, especially if blistering occurs. Oral or topical nonsteroidal anti-inflammatory agents (NSAIDS) have been used with some success in relieving symptoms presumably through inhibition of prostaglandins production.9 The application of topical corticosteroids can also help by inhibiting leukocyte migration or cytokine production. Using both NSAIDS and topical corticosteroids together can lead to synergistic effects in relieving sunburn symptoms.10 Finally, there is scientific investigation into the role of topical and oral antioxidants like vitamin E. It is possible that lowering the concentration of free radicals in UV injured skin will decrease the production of chemoattractants for leukocytes.11 Ultimately, sunburn avoidance through comprehensive photoprotection is the best goal to maintain healthy skin and a healthy future. REFERENCES 1. Wan S, Parrish JA, Jaenicke KF: Quantitative evaluation of ultraviolet induced erythema. Photochem & Photobiol 1983;37:643–648. 2. Parrish J. UVA: Biological Rffects of Ultraviolet Radiation with Emphasis On Human Responses to Longwave Ultraviolet. New York: Plenum Press, 1978. 3. Soter NA: Sunburn and suntan: Immediate manifestations of photodamage. In Gilchrest BA, (ed.) Photodamage. Cambridge: Blackwell Science, 1995:12–25. 4. Koh HK, Lew RA, Geller AC, Miller DR, Davis BE: Skin cancer: Prevention and control. In Greenwald P, Kramer BS, Weed DL, (eds.) Cancer Prevention and Control. New York: Marcel Dekker, Inc., 1995:611–640. 5. Goldsmith L, Koh HK, Bewerse B, et al: Proceedings from the national conference to develop a nation skin cancer agenda. J Am Acad Derm 1996;34:822–23. 6. Hebert AA: Photoprotection in children. Advances in Derm 1993;8:309–324. 7. Funk JO, Dromgoole SH, Maibach HI: Sunscreen intolerance: Contact sensitization, photocontact sensitization, and irritancy of sunscreen agents. Derm Clinics 1995;13:473–481. 8. Madronich S: The atmosphere and UV-B radiation at ground level. In Young A, Bjorn L, Moan J, Nultsch W, (eds.) Environmental UV Photobiology. New York: Plenum Press, 1993:1–39. 9. Lichtenstein J, Flowers F, Sheretz EF: Nonsteroidal anti-inflammatory drugs. Their use in dermatology. Internat J Derm 1987;26:80–87. 10. Hughes GS, Francom SF, Means LK, Bohan DF, Caruana C, Holland M: Synergistic effects of oral nonsteroidal drugs and topical corticosteroids in the therapy of sunburn in humans. Dermatology 1992;184:54–58. 11. Trevithick JR, Shum DT, Redae S, et al: Reduction of sunburn damage to skin by topical application of vitamin E acetate following exposure to UVB radiation: Effect of delaying application or of reducing concentration of vitamin E acetate applied. Scanning Microscopy 1993;7:1269–1281. |
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