Asthma is a chronic lung condition which is characterized by restricted airways, causing difficulty with breathing. The airways are affected by both tightening and inflammation of the muscles. This is often triggered by allergens (pollens, pet dander, moulds, etc.) as well as irritants (smoke, strong smells, cold air, etc.). Symptoms can include wheezing, coughing, shortness of breath, and feelings of tightness in the chest.