The exact cause of asthma is not known; there is not a single cause of asthma. The causes of asthma symptoms can vary for different people. Most often starts in childhood, and some researchers think genetic and environmental factors interact to cause asthma.
- Allergies – Exposure to allergens plays a causative role in the development of asthma.
- Asthma runs in families – Children who have a parent or sibling with asthma are 3- to 6-times more likely to develop asthma than children without a family history of asthma.
- Respiratory infections in childhood – Viral infections in infancy is a risk factor for development of asthma.