Abstract: 【Abstract】 Objective To investigate the protective effects of a sunscreen lotion containing Calendula extracts on children′s skin against sun exposure, as well as to evaluate its safety and tolerability when applied to children. Methods A single-center, randomized, split-body/face study was conducted on 200 healthy children aged 3 - < 18 years, who were enrolled from Beijing Children′s Hospital, Capital Medical University from July to August 2022. The participants were randomly and equally divided into Group A （the left side of the body/face applied with the test sunscreen, and the right side applied with the control sunscreen） or Group B （the right side of the body/face applied with the test sunscreen, and the left side applied with the control sunscreen） at a ratio of 1∶1. After applying the sunscreen, they were engaged in outdoor activities under sunlight. Skin tests were conducted on the temporal area, the extensor aspect of the upper arm and forearm before and after sun exposure. The test product was a mild sunscreen lotion containing Calendula extracts with the sun protection factor （SPF） being 50+ and the long-wave ultraviolet protection factor （PA） being +++, and the control product was a baby sunscreen containing licorice extracts （SPF35, PA++）. Bilateral differential scales were used to assess clinical symptoms after sun exposure, erythema values to clinically evaluate erythema after sun exposure, and the multifunctional skin testing platform MPA10 to measure melanin and erythema values, stratum corneum hydration, and transepidermal water loss （TEWL） at the tested sites. Related adverse events were observed and recorded during the study. The paired t-test or Wilcoxon signed-rank test was used for the comparison of quantitative data, and chi-square test （Fisher′s exact test） for the comparison of count data. Results Totally, 198 children completed the study and visits, including 100 males （50.5%） and 98 females （49.5%）, aged from 3 to 17 years （8.11 ± 0.23 years）, and there were 99 cases each in the Group A and Group B. The numbers of participants with more obvious sunburn symptoms after sun exposure in the 3 tested areas were all higher on the control side than on the test side （the temporal area: 11 cases vs. 4 cases; the extensor aspect of the upper arm: 16 cases vs. 2 cases; the extensor aspect of the forearm: 33 cases vs. 3 cases）, with significant differences between the bilateral sides （all P ＜0.001）. No significant differences were observed in the erythema values between the test side and control side in the 3 tested areas （all P > 0.05）. In the extensor aspect of the upper arm and forearm, the difference in the melanin value before and after sun exposure was significantly smaller on the test side （M ［Q1, Q3］: -0.33 ［-13.00, 14.17］, 1.17 ［-10.75, 12.67］, respectively） than on the control side （9.83 ［-8.50, 25.00］, 5.50 ［-4.08, 21.00］, respectively, both P < 0.001）, while the difference in the stratum corneum hydration before and after sun exposure was significantly greater on the test side （6.53［-2.12, 21.65］, 7.75［-4.08, 19.23］, respectively） than on the control side （2.35［-8.51, 14.44］, 1.35［-7.80, 12.37］, respectively, both P < 0.001）. However, there were no significant differences in the changes in the erythema or TEWL values before and after sun exposure between the test side and control side in either of the 3 tested areas （all P > 0.05）. During this study, 1 case （0.51%） experienced transient urticaria on the control side, and no serious adverse events occurred. Conclusion The mild sunscreen lotion containing Calendula extracts demonstrated superior efficacy to the control product in improving skin symptoms after sun exposure such as hyperpigmentation among healthy children aged 3 - < 18 years, with good tolerability and a relatively low incidence of adverse reactions.

Key words: Child, Sunscreening agents, Melanins, Erythema, Protective, Calendula flower extract