AD and Asthma Linked to Pet Ownership in Children with Mothers with Asthma

Researchers from Denmark found that having pets at home contributed to atopic dermatitis (AD) and asthma in the children of mothers with asthma.

The study was conducted to add to the limited amount of available data on the impact of perinatal and environmental factors on atopic diseases.

The study, headed by Zarqa Ali, also noted that children with AD have 3‐fold increased odds of developing asthma and rhinitis within a 5‐year period compared to children without AD, and that approximately 70% of patients with severe AD develop asthma compared with 20%–30% of patients with mild AD and approximately 8% in the general population.

A total of 571 pregnancies were included in the study.

Every mother in the study participated in the management of asthma during pregnancy (MAP) program from 2007-2015. They would later receive a reminder by letter from October 2017 to October 2018 to complete an online questionnaire about AD, asthma, and allergic rhinitis in the offspring.

Additionally, information on case history, tobacco exposure, exposure to pets at home, and pre‐pregnancy weight was collected at the first outpatient clinic visit. Subsequent visits included spirometry, fractional exhaled nitric oxide (FENO) and maternal body weight assessments.

A particular strength of the study was that all women who participated in the study were seen by the same pulmonologist, which the team of researchers claimed made the diagnosis of maternal asthma very reliable.

Of the total number of children, 113 had doctor-diagnosed asthma (21%), 178 (31%) atopic dermatitis, and 55 (32%) both AD and doctor-diagnosed asthma. Cases of AD were defined according to the U.K. Working Party definition.

The study found that cats were more commonly associated with asthma in child patients (OR, 2.16; 95% CI, [1.14–4.11]; p = .02) (Table 3) as well as and wheezing. Meanwhile, dogs were more commonly associated with AD in children (OR, 2.56; 95% CI, [1.40–4.67]; p = .002) as well as pre-pregnancy underweight.

Analysis was later repeated with women with more than one pregnancy and/or twin pregnancies. The results remained the same.

The investigators noted that in general 13% of all Danish children have AD. Additionally, 90% of homes in the United States have measurable levels of allergens related to cats and dogs, regardless of whether the homeowner has pets of their own.

Considering the worldwide prevalence of AD and pet ownership, researchers believed an increase in asthma linked to pets in children could be seen in the coming years.

However, researchers also mentioned finding contradictory evidence in their study and other studies.

“The studies exploring the association between pets and atopic diseases have been contradictory so far. Though, systematic reviews have reported reductions in the risk of atopic diseases among children with close contact with animals (farm animals or indoor pets) during infancy,” the researchers wrote. “However, regarding AD some studies have found a protective association of pets, and other studies with adjustment for avoidance behavior have not found this association.”

Reasons for the complications within the study could be linked to other known risk factors for asthma in children such as filaggrin gene mutations, ceramide deficiencies, a positive family history of atopic disease in either parent, obesity, and gestational weight gain.

However, not all previous studies that incorporate these risk factors came to the same conclusion regarding positive association in AD in children. These disparate findings, as well as a lack of literature on the subject, further elucidate the current study’s urge for more research.

Regardless, Ali and colleagues believed they had sufficient evidence in the present study to link child AD and asthma to having pets at home and called for further research on the subject.

“In the present study we found a positive association between having pets at home and developing AD and asthma. Furthermore, there was a positive association between pre‐pregnancy underweight and AD and ever wheeze in the offspring of mothers with asthma,” the team wrote. “Understanding these complex risk factors is crucial when clinicians are giving advice to prevent atopic diseases in genetic predisposed children. Future studies should investigate if removing pets from home before the birth and improvement of the maternal nutritional status before pregnancy can decrease the likelihood of AD and wheeze in the offspring.”

The study, “Associations between maternal and environmental exposures on atopic disease in the offspring of mothers with asthma,” was published online in Immunity, Inflammation, and Disease.