In the United States alone, more than 25 million individuals — including more than 4 million children — experience asthma, which is a chronic lung disease that can cause coughing, wheezing, chest tightness and shortness of breath. In severe cases, breathing becomes extremely difficult, and it feels like a weight compresses the chest. Worsening asthma can lead to missed time at school and work, emergency room visits and even death.