Asthma is caused by a combination of genetic and environmental factors. While it is inherited and runs in families, environmental triggers like allergens and irritants can cause asthma symptoms. Asthma is not communicable but is transmitted through genes. Anyone can develop asthma, though it often starts in childhood. Symptoms include coughing, wheezing, chest tightness and shortness of breath, especially at night or after exercise. Doctors diagnose asthma through medical history questions and lung function tests. Asthma is a lifelong condition, and while symptoms may subside during teenage years, it cannot be cured.