This 2021 human study investigated development and persistence of allergies:

“Allergic rhinitis (AR) is a common IgE-mediated disorder involving troublesome symptoms of nasal congestion, nasal itch, sneezing, and associated eye symptoms. Like many chronic health conditions, AR stems from complex gene–environment interactions.

130 subjects with AR were recruited. Control population included 154 healthy children who underwent a regular physical examination in the same ear, nose and throat clinic as AR patients. Individuals with history of asthma or atopic dermatitis were excluded.

Plenty of contradictory associations exist as whether furred pet exposure (cats and dogs) may be a risk or a protective factor for AR development. Discrepancies are likely due to the ubiquitous nature of pet allergens, while pet owners are more concerned about sanitation and many other hygiene-related reasons.

Interaction of early-life pet exposure with methylation level of ADAM33 increased the risk for AR onset 1.423 times more in children. This study provides evidence that:

• Early-life pet exposure and low methylation level of ADAM33 increase AR risk in children; and
• The interaction between pet exposure and methylation level of ADAM33 may play an important role in development of AR.”

https://aacijournal.biomedcentral.com/articles/10.1186/s13223-021-00526-5 “Interaction between early-life pet exposure and methylation pattern of ADAM33 on allergic rhinitis among children aged 3–6 years in China”

There’s nothing children can do about who their parents were. Exposing them to pet allergens, though, may be another example of early-life experiences causing lifelong effects.