Proximity of coniferous, mixed forests and agricultural areas was associated with elevated risk of eczema, especially in children who were born in the spring.

Greenness or the significant presence of living vegetation around the home in early childhood does not seem to protect children from atopic eczema, a new Finnish study shows. Instead, the proximity of coniferous, mixed forests and agricultural areas was associated with elevated risk of eczema, especially in children who were born in the spring.

“General greenness around the home did not protect children against eczema, which was contrary to our expectations and to the hypothesised allergy protective effect of nature contacts. Eczema is, however, only one of the allergic diseases in children, albeit generally the first to emerge,” says MD Minna Lukkarinen, a paediatric specialist from the FinnBrain Birth Cohort Study at the University of Turku, Finland, in a news release.

Atopic eczema occurs in 20–30 percent of children, and it is thought that urbanization and reduced biodiversity increase the risk of allergic diseases, but previous research findings on the topic are contradictory.

The present study analyzed material from six Finnish birth cohorts, involving a total of 5,085 children. In a birth cohort, the same children are followed-up from birth, which allows studying associations between environmental early-life exposures and the disease development prior to its onset. This study examined the associations between the season of birth, the greenness and land cover types, surrounding the early-life home, and the development of eczema by the age of two years.

“Although greenness around the home did not protect against eczema, surrounding vegetation can have other beneficial effects. We also must note that greenness is a rather rough measure of nature presence and relatively poor indicator of biodiversity. The observed predisposing association of coniferous forest may indicate that the effects of nature on child’s immunological development vary depending on the type of nature and the biodiversity and the exact timing of the exposures. Further studies are needed to confirm the result and to reveal the possible mechanisms,” says Anne Karvonen, the Chief Researcher at Finnish Institute for Health and Welfare (THL).

The study used data from the FLORA, LUKAS, STEPS, FinnBrain, Kuopio Birth Cohort, and HELMi cohorts from the University of Turku, THL, the University of Helsinki, the University of Eastern Finland, and the children's clinics of the central hospitals of Helsinki, Kuopio, and Turku. The study was based on the FINMIC collaborative project funded by the Academy of Finland. 

The study appears in Pediatric Allergy and Immunology.

Eczema continues to puzzle patients, clinicians, and researchers, says Peter A Lio, MD. He is a Clinical Assistant Professor of Dermatology and Pediatrics at Northwestern University's Feinberg Scjool of Medicine in Chicago. "The prevalence continues to increase, and environmental factors are increasingly understood to be involved in its development," he tells DermWire. "Recently there has been exciting literature suggesting that pollutants and chemicals in the environment likely damage the microbiome and the skin barrier--the two are deeply intertwined--and are linked to developing eczema."

This is different from the "hygiene hypothesis" that posited being too clean and lacking exposure to nature could alter the development of the immune system, he says. "In this paper, a meta-analysis of six Finnish birth cohorts comprising over 5,000 children, the authors conclude that more "greeness" (i.e., being surrounded by nature and ostensibly further from urban pollution) during early childhood did not seem to protect kids from developing eczema," he says. "Remarkably, nearby forests (specifically coniferous and mixed ones) actually seemed to increase eczema risk, which is honestly a bit surprising."

The bottom line? "We still have lots to learn about eczema."