Researchers at National Jewish Health in Denver have determined the time of year a baby is born may be a risk factor for allergic diseases.
The study aimed to understand why food allergies are on the rise with more than five million children in the U.S. now dealing with an allergy to at least one type of food.
Led by Dr. Jessica Hui, a pediatrician at National Jewish Health, the study’s investigators are working to discover what is responsible for the increase in food allergies, and have determined that many allergic conditions likely start with dry, cracked skin, which leads to a chain reaction of allergic diseases known as the atopic march.
“We looked at every child treated in our clinic, and those born in the fall were much more likely to experience all of the conditions associated with the atopic march,” said Dr. Hui, in a press release on Sept. 9, 2020. “Now we are learning more about why that is and we strongly believe it stems from the bacteria on the skin [and] how they affect the skin barrier.”
Children with eczema often have high levels of staphylococcus aureus (S. aureus) on their skin, which weakens the skin’s ability to keep out allergens and pathogens.
“When food particles are able to penetrate the skin rather than being digested, the body sees them as foreign and creates antibodies against them, which causes the child to become allergic,” Dr. Hui said.
For the study, published in The Journal of Allergy and Clinical Immunology (May 28, 2020; S2213-2198(20)30506-7), the National Jewish Health Research Database was queried to assess children under six years of age treated for respiratory, cardiac, immune and related disorders from February 2008 through August 2019.
Common childhood food allergy (FA) diagnoses were obtained using the International Classification of Diseases, Tenth Revision (ICD-10) codes and allergy history, including egg allergy (n=1,498), peanut allergy (n=1,870), and milk allergy (n=735). These specific FAs were chosen as they are the most common FAs in children.
The researchers also assessed the diagnoses of atopic dermatitis (AD) (n=5,378), AD without FA (n=2,651), AD with FA (n=2,727), AD with FA and asthma (n=1,010), AD and asthma without FA (n=892), AD with FA, asthma, and allergic rhinitis (AR) (n=594), AD with asthma and AR without FA (n=376), AD with positive S. aureus skin cultures (n=468), and AD with FA and positive S. aureus skin cultures (n=339). These diagnoses were obtained using ICD-10 codes, and positive S. aureus skin cultures were extracted from the electronic medical record.
Researchers used a conservative one-sided 99% confidence interval to evaluate if there was a greater proportion of fall births (individuals born in September, October, and November) compared with the other three seasons in individuals with atopic diseases.
During the study period, the investigators saw 14,877 unique patients under six years at the National Jewish Health clinics. There was no significant finding of season of birth, nor was there a significant difference in demographics based on race, gender, and age of the first visit.
In children five years old and younger, the common FAs of egg, peanut, and milk were more prevalent in those born in the fall. Researchers found there was no fall birth association in AD without FA.
The investigators saw a higher prevalence of fall birth in children five years old and younger with AD and skin cultures positive for S. aureus.
Researchers are now conducting a clinical trial to look at a variety of factors that may contribute to this weakened skin barrier in babies. They are enrolling pregnant women and following their babies into early childhood to consider everything from environmental factors to genetics to medications taken and products used in the home.
The researchers hope this will help explain why babies born in the fall are at greater risk and help develop solutions to stop the atopic march in its tracks.
“We think if we can intervene at a very young age, even right after the baby’s out of the womb, then potentially that’s a way for us to try to stop the development of this atopic march,” Dr. Hui said.