To protect children from asthma and hay fever, parents may need to fill their house with pets. Every extra dog or cat in the house reduces a child’s chance of getting an allergic disease by a fifth, a study has found.
The danger is lowest for children who grow up with five or more pets, probably because of the bugs the animals carry. Scientists say a large number of pets may have a ‘mini-farm’ effect, as children who grow up close to cattle on farms also tend to have a lower risk of allergic conditions.
The microbes found on animals are believed to trigger an infant’s immune system. Researchers studied more than 1,200 children aged seven to nine, recording how many pets they had in their first year of life and if they had asthma, eczema or hay fever.
The results show children with no pets had a 49 per cent higher risk of these conditions, suggesting animals in the house could protect them.
The study, led by Dr. Bill Hesselmar from the University of Gothenburg, states: ‘The prevalence of allergic disease in children aged seven to nine years is reduced in a dose-dependent fashion with the number of household pets living with the child during their first year of life, suggesting a ‘mini-farm’ effect, whereby cats and dogs protect against allergy development.’
Cats and dogs carry microbes which may cause the immune system to function properly, so that it does not overreact to triggers like pollen. Researchers also looked at children’s medical records or questioned parents on whether they had ever suffered from hay fever, asthma or eczema and many cats and dogs youngsters had lived with in their first year of life.
The results, published in the journal PLOS One, show each additional pet cut a child’s risk of an allergic condition by 20 per cent. This was the case for children clinically tested for the diseases and those whose parents reported they had them.
The risk of ever having had an allergy was 49 per cent higher in families with no pets, but plummeted for those with five or more.
The findings back up the ‘hygiene hypothesis’ that the immune system must be exposed to bugs so it is ‘trained’ to ignore harmless things like pollen and peanuts and people do not develop allergies.
Dr. Hesselmar said: ‘Our hypothesis is that the protection is due to exposure to microbes and microbial products, i.e. the hygiene hypothesis, and that more animals will lead to increased exposure.’
The study concludes: ‘Most often research focus on identifying risk factors for allergy development. But in modern society, finding lifestyle factors that could protect from allergy has become equally important.’