Years ago, it was believed that children develop allergies if they grow up with pets in the home. Since then, many studies have shown that the opposite is true. Children raised with pets have a lower risk of developing allergies later in life.
Bill Hesselmar and his team from the University of Gothenburg in Sweden have gone a step further, demonstrating that the allergy risk decreases further as the number of animals in the home increases.
How did the team conduct the study?
The scientists looked at two groups:
- They analysed 1,029 allergy questionnaires from children aged seven and eight. One group of children lived in the area surrounding the major city of Gothenburg. The second group lived in Kiruna, a small town in the far north of Sweden.
- They examined the data from two earlier studies. One study focused on children from a city near Gothenburg. The second focused on children from rural areas, some of whom grew up on farms. The pulmonary function of the children was tested. Their blood was also tested for certain immune system cells.
This time, Hesselmar and his team asked all 249 children from both studies whether they kept pets in the home.
What were the findings of the study?
The more dogs and cats the children had in their environment during the first year of life, the less often allergy symptoms occurred. The researchers searched for asthma, eczema and allergic rhinoconjunctivitis, whose symptoms include red, swollen and itchy eyes and a runny, itchy nose.
In the first group, 49% of children without pets developed allergy symptoms at some point. On the other hand, children in homes with five or more pets never had allergies. The research team also asked about allergies in the previous year and found that 32% of children without pets had one allergy while children with five or more pets had none.
The results were similar in the second group.
How can the findings help?
Hesselmar believes that the presence of several animals has a ‘mini-farm’ effect on the children, as if they were living on a sort of small-scale farm. This means that the children come into contact not only with the animals but also with other microorganisms and additional factors, such as airborne particles, that have an impact on the immune system. These factors train the children’s immune system, which protects them from allergies later in life, not only to animals but also to other potential allergens, such as pollen.