EXPOSURE TO ANIMALS
Using the same study population, a previous study by Dr. Roduit and colleagues showed that prenatal exposure to farm animals was associated with a lower risk of atopic dermatitis. The new study showed that prenatal exposure to farm animals tended to protect against the development of all atopic dermatitis phenotypes.
But for household pets, that protective effect of prenatal exposure was seen only in children with the early persistent phenotype, specifically, among children with allergic parents.
For children who have a parent with a history of allergy, prenatal exposure to both a dog and a cat was found to be negatively associated with the early-persistent phenotype. This was surprising, Dr. Brar said, “because we typically think of cat allergies as being particularly bad due to the small molecular size and buoyancy of the allergen.”
STRENGTHS AND LIMITATIONS
Strengths of the study included its large birth cohort and its length: Data was collected prospectively from birth to school age, which allowed researchers to use latent class analysis (LCA) to identify disease phenotypes by onset and progression. Also, SCORAD (Scoring atopic dermatitis) was performed to corroborate phenotype data in the study sample.
The study had some limitations. It did not focus on biomarkers which may have helped distinguish phenotypes, Dr. Brar said. Additionally, asthma and food allergies were diagnosed based on the parental report of a physician diagnosis. “Food allergies were not verified by an observed food challenge, which is the gold standard for diagnosis, Dr. Brar said.
“We should expect to see more studies examining the relationship between atopic dermatitis and food allergy with a focus on prevention strategies such as the Learning Early About Peanut Allergy (LEAP) guidelines,” Dr. Brar says.
The study’s findings may not be generalizable to all populations because the study included data on only children from rural regions of Europe.
Roduit C, Frei R, Depner M, et al. “Phenotypes of atopic dermatitis depending on the timing of onset and progression in childhood,” JAMA Pediatrics. July 1, 2017. DOI:10.1001/jamapediatrics.2017.0556 Online at: bit.ly/2k8Ki9g