During an asthma attack, the muscle around the airway contract, tissues are swollen, and massive mucus is secreted due to the inflammatory process. All these changes lead to a narrow airway and cause symptoms of wheezing and breathlessness. Triggers of asthma vary across individuals. They can generally be viral infections, allergens (pollens, dust), food allergies, air pollutants, cold weather, poor medication adherence, exercise and mental stress.