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Sunscreens, physical barriers partially effective in preventing UVB effects on nevi
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Physical barriers and sunscreens each provided partial protection in preventing ultraviolet B effects on nevi, according to recent study results.
Researchers studied 23 nevi located on the trunk of 20 patients (mean age, 36.5 years; 60% women) attending a referral hospital in Barcelona, Spain. Nevi had diameters greater than 5 mm, at least 1 axis symmetry and no suspicion of melanoma. The nevi were divided into two groups. Half of each nevus in one group (n=14) was covered with an opaque barrier before irradiation, while in the other group (n=9), half of each nevus was protected by 2 mg/cm2 of topical sunscreen (SPF 50) and the remaining half was covered by a patch to avoid cream diffusion.
Before and 7 days after one dose of ultraviolet B (UVB) irradiation cleared all lesions and excision occurred, in vivo examination was conducted, including histopathologic and immunohistochemical studies.
Increased pigmentation (61%), surface scaling (57%) and erythema (57%) were the most frequent clinical changes after UV radiation. Increases in dotted vessels in the nevus and surrounding skin (30%), presence of diffuse erythema (43%), changes in size of globules and dots (9%) and increases in the regression structures (43%) were the most frequent dermoscopic changes.
Varying degrees of change occurred in the physical barrier- and sunscreen-protected areas. Clinical examination showed that 30% of nevi did not display any change; 18% showed no dermoscopic change.
“Parakeratotic scale, increased number and activation of superficial melanocytes and keratinocyte proliferation were the most remarkable features,” the researchers reported.
The sunscreen-protected lesions displayed more enhanced melanocytic activation and regression features compared with the physical barrier-protected lesions. The researchers found no phenotypic features to predict a specific UVB response.
“Subclinical UV radiation effects, not always associated with visible changes, can develop even after protection,” the researchers concluded. “Sunscreens are not quite as effective as physical barriers in the prevention of inflammatory UVB-induced effects.”
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