Asthma is a common condition that affects your lungs. Asthma can cause your airways to become irritated and swollen and this can affect how well you can breathe. The causes of asthma are not fully understood. But asthma symptoms can be made worse by many triggers such as household dust or cleaning products, pet dander or air pollutants. There is no cure for asthma. However, there are several treatments as well as simple advice on how to manage this long term condition.