An incurable condition that affects the airways – the small tubes that carry air in and out of the lungs. An asthma attack can be triggered when a person with asthma comes into contact with something that irritates their airways (an asthma trigger, such as pollen or dust mites). Then the muscles around the walls of the airways tighten so that the airways become narrower and the lining of the airways becomes inflamed and starts to swell. Symptoms of the narrowing include wheezing, chest tightness, breathing problems, and coughing. Environmental factors such as pollen, dust mites, pollution, ozone levels and high levels of humidity are important, and genetic factors are also involved, though much work remains to be done for greater understanding of these hereditary factors to be reached.