What do we know about development of asthma?

Asthma affects different people in different ways, which is one reason why it is so hard to define and diagnose. But research is showing us that the process that leads to asthma starts very early in life – possibly before birth – and involves a complex interaction between genetic and environmental factors.

Recent studies indicate that young children who are prone to asthma because their parents have allergies or asthma are likely to have lower lung function than normal even if they show no signs of wheezing or other asthma symptoms. This suggests that the process of asthma development is well under way in the early years of life, when the lungs develop most rapidly.

There is much we still don’t know, especially about the environmental factors that contribute to asthma. Research is finding some clues, particularly about tobacco smoke, allergies, and the possible protective effect of infections.

Tobacco smoke and a baby’s lungs

Exposure to tobacco smoke affects lung development before and after birth. While tobacco smoke does not cause asthma itself, it does increase the risk of transient wheeze, affects airway growth and can induce asthma attacks in children with asthma.

Women should not smoke while pregnant. Exposure of babies and children to tobacco smoke should also be avoided.

Infections, wheezing and asthma

Infections such as bronchiolitis are the main cause of transient wheezing, and conditions that increase exposure to infections (such as having more brothers and sisters or being in child care) are risk factors for transient wheezing.

On the other hand, these same factors seem to protect children against persistent wheezing.

Children who have frequent colds and other common infections as babies are less likely to develop persistent wheezing in later childhood.

It is thought that common childhood infections may change children’s immunity so they are less susceptible to allergic responses such as inflammation. More research is needed to explore this further.

Asthma and allergies

The link between allergies and asthma is complex. See the ‘Asthma and Allergies’ and ‘Asthma and Infant Bedding’ brochures for more information.

What is asthma?

Asthma is a reversible narrowing of the airways in the lungs. Asthma symptoms include wheezing, coughing (particularly at night), chest tightness, difficulty in breathing and shortness of breath.

Asthma is a manageable health condition. Although at the moment there is no cure, with good management people with asthma can lead normal, active lives.

Main messages

Wheezing is very common in the first few years of life but more than half of all children who wheeze do not develop asthma.
Asthma is more likely to develop in children who continue to wheeze beyond the age of three and have allergies, or have parents with allergies or asthma.
The process that leads to asthma starts very early in life – possibly before birth – and involves a complex interaction between genes and the environment.
Exposure to tobacco smoke affects lung development before and after birth. Women should not smoke while pregnant. Exposure of babies and children to tobacco smoke should be avoided.