Is Decreased Ultraviolet Exposure During Childhood the Cause of the Increased Prevalence of Atopic Dermatitis?

Abstract

There is a recent accumulation of data suggesting that decreased exposure to ultraviolet light in childhood could be a major factor contributing to the increasing rates of atopic dermatitis in children and adolescents. It would be worthwhile to study the relationship between vigilant sun protective behaviors in children and the incidence of atopic dermatitis.

It is a well-established fact that sun exposure and ultraviolet A/ultraviolet B phototherapy are beneficial for patients with a diagnosis of atopic dermatitis,1 so it is no surprise that there is a growing body of evidence that ultraviolet-induced immunomodulation or a lack thereof is playing a roll in the increasing prevalence of atopic disease both in the United States and other countries.2,3 In addition, a recent study found an association between increased sun exposure and a reduced risk of atopic dermatitis in children and adolescents.4

The data in the United States and worldwide show a steady increase in the rates of atopic dermatitis in children, and one must wonder if the vigilant use of sunscreen and sun avoidance in children as recommended by the American Academy of Pediatrics5 is one of the underlying reasons behind this trend. An article in Pediatrics looking at office visits for atopic dermatitis as a surrogate for the prevalence of atopic dermatitis in a patient population from newborns to age 18 throughout the United States from 1997 to 2004 showed a statistically significant increase in the number of visits over time even though the number of office visits for all diagnoses remained stable.6 It appears that as sunscreen use for children has become more widespread in the United States, the number of children diagnosed with atopic dermatitis has increased as well.

Multiple studies have found that atopic eczema is more prevalent in affluent children.7-12 The literature shows that this same population of individuals with higher socioeconomic status in the United States and other countries is also more stringent about sun protective behaviors.13-14 As one might expect given the findings from studies on socioeconomic status, people with lower socioeconomic status living in rural areas are both less likely to engage in sun-protective behaviors and less likely to develop atopic dermatitis.15 A multitude of studies show that growing up on a farm protects against the development of allergic disease,16-23 which taken together with the other literature on socioeconomic status supports our hypothesis that increased time outdoors, decreased sun-protective behavior, and thus increased exposure to ultraviolet light decreases the incidence of atopic disease. One might infer that the trend toward children spending less time outdoors and more time inside watching television and playing video games is also directly affecting the increase in atopic disease.

Given the recent accumulation of data regarding the relationship between atopic disease and ultraviolet-induced immunomodulation, the authors believe the question of if ultraviolet avoidance in childhood increases the risk of atopic dermatitis deserves additional study. If there does appear to be a correlation, we should consider whether we need to create less stringent guidelines for ultraviolet avoidance.