Why Colds Can Raise Babies’ Risk Of Asthma

Children who catch a heavy cold at key moments during their first year of life are at greater risk of developing asthma, researchers have found.

Children who catch a heavy cold during their first year of life are at greater risk of developing asthma, researchers have found more than a million children suffer from asthma in Britain, and the number is rising.

Scientists at Imperial College London have discovered that if infants are exposed to allergens such as dust or pollen while infected by viruses such as the common cold, it can leave them more susceptible to asthma attacks.

They believe the viruses “trick” the immune systems of young children into thinking that allergens are a threat when youngsters encounter them for the first time. This wrong “first impression” leaves children highly sensitive to the particular allergen, causing asthma attacks when their bodies react violently to any subsequent exposure.

The findings appear to contradict previous research which suggested that regular infections help protect children by allowing them to develop a healthy immune system. Experts had feared that over-cleanliness might be a cause of the soaring British asthma rate.

Prof Sebastian Johnston, a lecturer on respiratory medicine at Imperial College who took part in the research, said: “If you are exposed to an allergen for the first time, the body usually becomes tolerant of it. There is also pretty clear evidence that infections in general are likely to protect you from developing allergies.

“What we have found is that there is a strong relationship between children who suffer respiratory illness early in life and the risk of them developing asthma later. It may be a matter of bad timing, so that if a child is exposed to an allergen at the same time as a virus infection, then the child might become sensitised to that allergen instead of being tolerant of it.”

Prof Johnston and a team of scientists at the University of Western Australia in Perth studied almost 200 children for five years, recording the viruses they were infected by and when they developed allergies. They found that children were up to three times more likely to suffer from asthma at the age of five if they had suffered a severe infection in their airways and developed sensitivity to an allergen within a short space of time in their first year.

However, experts also believe there is a strong genetic element that may leave children more vulnerable to this effect, while other research has suggested that pollution and diet also play a role.

Asthma attacks are caused by irritation of the airways by dust, pollution or other particles, which causes the muscles in the airway to tighten and become inflamed, making it difficult to breathe.

Prof Johnston believes that by identifying “high risk” children with a family history of allergies and protecting them from the effects of severe respiratory viruses during infancy, it may be possible to reduce the risk of developing asthma.

Britain has one of the highest rates of asthma in the world with more than 5.2 million people suffering from the illness. That figure includes about 1.1 million children.

The House of Lords is holding an inquiry into asthma and allergies.