Research Update: Sunscreen Accumulation and Thickness Influence UV Protection

Sunscreen Application Levels For Proper Accumulation Determined

New results suggest that the efficacy of sunscreens in filtering daily exposure to UV radiation is greatly increased with multiple applications per day and on consecutive days. Researchers used two sunscreens on 22 volunteers on five consecutive days, once daily (12 volunteers) and three times daily (10 volunteers). They determined SPF on days one, three, and five. While one daily application of sunscreen did not result in an accumulation in the skin that significantly affected the SPF, three daily applications provided a significantly higher SPF for both organic and particle sunscreens at day five compared to day one.

—Photodermatol Photoimmunol Photomed. 2012; 28(3): 127-32.

Correlations Between Use of Sunless Tanners and Tanning Behaviors

New data indicate that sunless tanning product use is associated with decreased UV radiation tanning frequency in women, particularly for those who use the products repeatedly. Investigators conducted a cross sectional study and found that 48 percent of participants had used sunless tanning products, 70.6 percent had tanned in the sun, and 26.0 percent had used tanning beds at least once in the past year. Most participants (92.7 percent) believed that tanned skin is more attractive than untanned skin, and 79.2 percent reported feeling better about themselves when tan.

Many sunless tanning product users reported decreased frequency of tanning in the sun (36.8 percent) or in tanning beds (38 percent) because of product use. Frequent users were more likely to have decreased their UV radiation exposure. Lighter complexion, frequent use of UV radiation tanning methods, feeling better about oneself when tan, and having a history of skin cancer were independently associated with sunless tanning product use. The researchers concluded that improvements in the appearance of sunless tanning product tans may allow wider acceptance by the public and further decreases in UV radiation tanning practices.

—Arch Dermatol. 2012; 147(4): 448-54.

Link shown Between Vitamin D Production and Sunscreen Thickness

Vitamin D production increases exponentially when thinner suncreen layers than the World Health Organization recommends are applied to the skin, new findings suggest. Researchers evaluated 37 healthy volunteers with fair skin types, who were randomized to receive an inorganic sunscreen SPF 8 of 0mg/cm2, 0.5mg/cm2, 1mg/cm2, 1.5mg/cm2, or 2mg/cm2 on the upper body (approximately 25 percent body area). Participants were irradiated with a fixed UVB dose of three standard erythema doses 20 minutes after sunscreen application. This procedure was repeated four times with a two-to-three day interval. Researchers found that for all layers of sunscreen, the level of 25(OH)D increased significantly after irradiation, except for the group treated with 2mg/cm2, in which the increase in 25(OH)D was not statistically significant. The researchers concluded that re-evaluation of sun protection strategies could be warranted.

—Br J Dermatol. April 18, 2012