Will my kids inherit my asthma?

About half of all kids with asthma no longer have it by the time they grow up. Even some adults outgrow it later in life, particularly if they have a mild case of asthma.

Asthma does tend to run in families.¹ If your parents had asthma, you are more likely to have asthma too. What this means is that there is increased risk of your children developing asthma.

So is it genetic? Or do asthmatic families live in areas that can cause asthma? In other words, are genes, the environment, or a combination of the two involved?

To try to figure out what role the environment plays, scientists often do a twin study. In a twin study, identical twins are compared to fraternal twins.

If something happens more often in identical twins, then there are probably genes involved. If something happens to only one identical twin, then there may be something in the environment doing something. And if both are true, then both the environment and genes play a role.

Why do twin studies work? Because the twins in an identical twin pair have exactly the same genes. Fraternal twins share only as many genes as any brother or sister. So if something were purely genetic, then if one identical twin has it, the other twin should have it as well.

Many twin studies have shown that both genes and the environment were important in asthma.² Identical twins are more likely to have asthma than fraternal twins. This means that genes play a role.

However, sometimes only one twin in an identical twin pair has asthma. Since they share the same genes, this means that something in the environment must be playing a role too.

These sorts of results are pretty typical for complex diseases like asthma. There probably isn’t a single gene involved nor will every case of asthma be caused by the same set of genes. In asthma, something in the environment causes the body’s immune system to overreact causing, among other things, shortness of breath.

The immune system is so complex that there are lots of different genes involved in making it work right. Lots of immune genes can lead to asthma when they don't work properly.

With such a complex disease and so many triggers, it probably isn’t surprising that there are so many potential asthma genes out there. Maybe one day scientists will be able to look at someone’s genes and tell if they are likely to get asthma. In the meantime, we can do whatever we can to limit our exposure to triggers.