For families with children with asthma, live with a cat in the home It is usually a cause of doubt and concern. Scientists at Sweden’s Karolinska Institute offered evidence that could guide that conversation.

Living with cats was not associated with more asthma attacks or greater asthma severity in children with a confirmed diagnosis. That is the central finding of the research, published in the journal Frontiers in Allergy, which adds to the debate about pets and childhood asthma.

The study, however, did not have data on whether the children were specifically allergic to cats, an issue that the scientists themselves acknowledged as a limitation.

The research was carried out by Reshie Putri, Cecilia Lundholm and Catarina Almqvist, among other colleagues from the Karolinska Institute and the Karolinska University Hospital of Swedenwith the participation of the Center for Infectious Diseases Research in Zambia.

Asthma is one of the most common chronic diseases in childhood, and factors in the home environment occupy a central place in its management. The presence of cats generates constant questions in pediatric consultations.

Most previous studies focused on early exposure: whether owning a cat during the first years of life increases the risk of developing the disease. On the other hand, what happens with children who already have asthma and live with cats was much less explored territory.

Existing studies on this group yielded contradictory results, with small samples and self-reported data. That left a question with direct implications for thousands of families without a clear answer.

The research aimed to determine whether exposure to cats affects the evolution of asthma in children with an established diagnosis. The scientists examined four variables: frequency of asthma attacks, disease severity, asthma control and lung function.

They also wanted to know if the characteristics of the animal—how many cats there are at home, whether they are male or female, young or old—in any way influence the results.

The hypothesis was that different cat profiles could generate different levels of allergens and, therefore, different effects on asthma.

The work targeted a group of Swedish children between 4 and 17 years old, all with a validated medical diagnosis, to obtain results applicable to real clinical practice.

The researchers conducted the cohort study based on Swedish national registries. The sample included 30,277 children born between 2006 and 2020, with a proven diagnosis of asthma and allergies.

Cat exposure was defined as recorded ownership of at least one cat in the household in 2023, according to the National Cat Registry.

Follow-up spanned 2023-2024 and measured whether the child had an asthma attack—emergency visit or frequent use of rescue bronchodilators—and whether they had moderate to severe asthma.

A subgroup of 1,428 children also had their lung function assessed using spirometry, a test that measures how much air a person can expel in one second.

Of the 30,277 children, 9.4% lived with at least one cat. Asthmatic attacks occurred in 3.3% of children with a cat and in 3.5% of those without.

Moderate to severe asthma affected 9.6% of the first group and 10.1% of the second. No difference was statistically significant.

In the subgroup with lung function data, the proportion of uncontrolled asthma was somewhat lower among those who lived with cats—16.5% versus 22.3%—but it did not reach statistical significance either. Neither spirometry nor the asthma control test showed differences between the groups.

Within the group with cats, it did not matter how many animals were in the house, whether they were male or female, or their age: no variable was associated with worse asthmatic outcomes.

The researchers noted that “no association was observed between exposure to cats and asthma exacerbations, severity, lung function, or asthma control.”

They highlighted that the findings “suggest that exposure to cats may not negatively affect asthma outcomes in this population.”

The study acknowledged that data were not available on specific sensitization to cat allergens or on the length of time the animal had been in the home.

The national cat registry also does not have full coverage, so some children with cats could have been misclassified as not exposed.

The researchers cautioned that the results apply to allergic asthma and not other types, and that cultural differences between countries may limit their generalizability.

In dialogue with Infobaethe doctor Pablo Morenoformer president of the Argentine Association of Allergy and Clinical Immunology (AAAeIC), said: “The new study shows that living with cats did not worsen asthma in children. Pets often play a very important role in homes and this study is encouraging.”

However, the expert suggested that families be cautious because “each individual may have different forms of sensitization. The work also does not address whether there is a relationship with rhinitis or conjunctivitis, among other conditions.”

According to Moreno, “you should learn to live with the cat. The animal should not sleep in the same room as people. Its litter tray should be far away and it should be bathed periodically, not for the cat but for the patient with asthma.”