Knowing if you or a loved one has asthma can be a tricky process. It can especially be difficult to determine in children under the age of 5. Using symptoms as a guide is not a fool proof way of determining if a person has asthma or not. A doctor is best suited to determine how well lungs are working. The doctor will find out if you cough often at night, if breathing is difficult after physical activity or at certain times of the year. Using various questioning techniques and an instrument called a spirometer, the doctor can determine air flow percentages which can help with a proper asthma diagnosis. A correct diagnosis of can determine the next course of action to control asthma symptoms during the troublesome times of the year.