UV Light Linked to Prevention of Allergic Disease in Infants

Marcia Frellick

July 12, 2021

Higher direct ultraviolet (UV) light exposure in the first 3 months of life was linked to lower incidence of proinflammatory immune markers and lower incidence of eczema in an early-stage double-blind, randomized controlled trial.  

Kristina Rueter, MD, with the University of Western Australia in Perth, who presented her team's findings on Sunday at the European Academy of Allergy and Clinical Immunology (EAACI) Hybrid Congress 2021, said their study is the first to demonstrate the association.

"There has been a significant rise in allergic diseases, particularly within the last 20-30 years," Rueter noted.  

"Changes to the genetic pool take thousands of years to have an impact," she said, "so the question is why do we have the significant, very recent rise of allergic diseases?"

Suboptimal vitamin D levels during infancy, lifestyle changes, nutritional changes, and living at higher latitudes have emerged as explanations.

In this study, 195 high-risk newborns were randomized to receive oral vitamin D supplements (400 IU/day) or placebo until 6 months of age.

Researchers found that UV light exposure appears more beneficial than vitamin D supplements as an allergy prevention strategy in the critical early years of immune system development.

The researchers used a novel approach of attaching a personal UV dosimeter to the infants' clothing to measure direct UV light exposure (290-380 nm). Vitamin D levels were measured at 3, 6, 12, and 30 months of age. Immune function was assessed at 6 months of age, and food allergy, eczema, and wheeze were assessed at 6, 12, and 30 months of age.

At 3 (P < .01) and 6 (P = .02) months of age, vitamin D levels were greater in the children who received vitamin D supplements than those who received placebo, but there was no difference in eczema incidence between groups. The finding matched those of previous studies that compared the supplements with placebo, Rueter said.

However, infants with eczema were found to have had less UV light exposure compared to those without eczema (median interquartile range [IQR], 555 J/m2 vs 998 J/m2; P = .023).

"We also found an inverse correlation between total UV light exposure and toll-like receptor cytokine production," Rueter said.

"The more direct UV light exposure a child got, the less the chance to develop eczema," she said.

Researchers then extended their analysis to see whether the effect of direct UV light exposure on reduced eczema would be maintained in the first 2.5 years of life, "and we could see again a significant difference that the children who received higher UV light exposure had less eczema," Rueter said.

Barbara Rogala, MD, PhD, professor at the Medical University of Silesia in Katowice, Poland, told Medscape Medical News that, just as in studies on vitamin D in adult populations, there must be a balance in infant studies between potential benefit of a therapeutic strategy of vitamin D and sunlight and risk of side effects. (Rogala was not involved in Rueter's study.)

Although vitamin D supplements are a standard part of infant care, exposure to sunlight can come with cancer risk, she noted.

Rueter agreed caution is necessary.

"You have to follow the cancer guidelines," she said. "Sunlight may play a role in causing skin cancer, and lots of research needs to be done to find the right balance between what is a good amount which may influence the immune system in a positive way and what, on the other hand, might be too much."

As for vitamin D supplements, Rueter said, toxic levels require "extremely high doses," so with 400 IU/day used in the study, children are likely not being overtreated by combining sunlight and vitamin D supplements.

The study was supported by grants from Telethon–New Children's Hospital Research Fund, Australia; Asthma Foundation of Western Australia; and the Princess Margaret Hospital Foundation, Australia. Rueter and Rogala have reported no relevant financial relationships.

EAACI Hybrid Congress 2021. Presented July 10, 2021. Abstract LB OAS 01.

Marcia Frellick is a freelance journalist based in Chicago. She has previously written for the Chicago Tribune, Science News, and Nurse.com, and was an editor at the Chicago Sun-Times, the Cincinnati Enquirer, and the St. Cloud (Minnesota) Times. Follow her on Twitter at @mfrellick

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