Impact of solar ultraviolet radiation on atopic dermatitis symptoms in young children: A longitudinal study.

BACKGROUND: There are controversial data about the effects of sun exposure on atopic dermatitis (AD). We evaluated the association between solar ultraviolet radiation (UVR) exposure and AD symptoms in children.

METHODS: Eighty-two children under 6 years (48 boys and 34 girls) with AD living in Seoul, Korea, were enrolled and followed for 12 months between September 2013 and August 2014. Daily symptoms were recorded to describe the degree of itching, sleep disturbance, erythema, dryness, oozing, and edema. We assessed solar UVR by measuring radiation heat flux over the 290-400 nm wavelength range using thermopiles. A generalized linear mixed model and a generalized additive mixed model were used to evaluate the effects of UVR exposure on AD symptoms after adjusting for age, sex, outdoor temperature, outdoor humidity, and ambient air pollution.

RESULTS: Symptom records of 12 915 person-days were analyzed. UVR showed a significantly positive relationship with AD symptoms. Over the study period, an increase in UVR by 10 W/cm2 was associated with a 1.46% increase in AD symptoms (95% CI: 0.85-2.07) on the exposure day. An increase in the 6-day average level of UVR of the previous 5 days and the current day by 10 W/cm2 was associated with a 3.58% (95% CI: 2.60-4.56) increase in AD symptoms. UVR exposure significantly increased AD symptoms in autumn, but decreased them in winter.

CONCLUSIONS: Atopic dermatitis symptoms in children are likely to be affected by exposure to solar UVR with a cumulative effect, and this effect is different according to season.