Babies who grow up around dogs less likely to develop asthma

By Stephen Beech

Babies who grow up around dogs are less likely to develop childhood asthma, according to new research.

But growing up with cats does not seem to have the same effect, say scientists.

Researchers found that babies exposed to dog allergens in the home have a lower risk of developing asthma by five years of age.

The research team from The Hospital for Sick Children in Toronto, Canada, also studied babies’ exposure to cat allergens, but did not find the same protective effect.

Team member Dr. Jacob McCoy said: "Asthma is a very common chronic respiratory illness in children, with the highest rates in the first four years of life.

"It is caused by complex interactions between genetic factors and the environment, including infections, allergies and air pollution.

“Children spend most of their time indoors, so in this research, we wanted to study allergens in the home.

"These are an important risk factor that we could potentially alter to reduce asthma.”

Researchers analyzed samples of dust from the homes of 1,050 children taken when they were between three and four months old.

For each child, researchers measured the quantities of three potential allergens in the dust: Can f1 - a protein shed in dog skin and saliva;, Fel d1 - a protein shed in cat skin and saliva; and endotoxin - a molecule on the surface of bacteria.

When the children were five years old, they were assessed for asthma by a doctor, and their lung function was measured according to how much air they could blow out in one second after a deep breath.

The children also gave blood samples so they could be assessed for genetic risk factors for asthma and allergies.

The research team found that babies exposed to higher levels of the dog allergen Can f1 had around a 48% lower risk of developing asthma by the age of five, compared to other babies.

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Babies exposed to higher levels of dog allergen also had better lung function.

The protective effect was even stronger in babies who were at higher genetic risk of worse lung function, according to the findings.

But the researchers found no protective effect for babies exposed to the cat allergen Fel d1 or the bacterial endotoxin.

Dr. McCoy said, “In this study, we examined pet allergens from dogs and cats.

"We found that, while cat allergens showed no association, exposure to dog allergens was linked to improved lung function and a reduced risk of asthma.

"We don’t know why this happens; however, we do know that once a person becomes sensitive to dog allergens, they can make asthma symptoms worse.

"This suggests that early exposure to dog allergens could prevent sensitization, perhaps by altering the nasal microbiome – the mixture of microbes living inside the nose – or by some effect on the immune system."

He added: "Our findings highlight the potential protective role of dog allergens, but we need to do more research to understand the link between early-life exposure to dog allergens, lung function and asthma during early childhood.”

Dr. McCoy is due to present the findings at the European Respiratory Society (ERS) Congress in Amsterdam on Sunday, September 28.

Professor Erol Gaillard, Chair of the ERS expert group on paediatric asthma and allergy, welcomed the findings.

Professor Gaillard, from the University of Leicester, who wasn't involved in the study, said: “Asthma is the most common long-term condition among children and young people and is also one of the main reasons for children being admitted to hospital for emergency treatment.

"Although there are good treatments that can reduce or stop asthma symptoms, we also want to reduce risk factors to try to prevent asthma.

“This study suggests that babies who grow up around dogs may have a lower risk of developing asthma."

He added, "This is potentially good news for families with pet dogs.

"However, we need to know more about this link and how living with pets affects children’s developing lungs in the longer term.”