If you have a cough that won't go away, you may have asthma. A chronic cough is one of the symptoms of asthma. For some people, a cough may be their only asthma symptom.

Asthma is a chronic, or ongoing, lung disease marked by inflammation and swelling of the airways in your lungs. When you have an asthma attack, your airways overreact to certain triggers, such as exercise, a cold, dust or pollen. This reaction causes inflammation, irritation, swelling, and tightening of your airways, making breathing difficult.
When your airways are inflamed, it makes it hard for air to flow into your lungs. This can cause coughing and other asthma symptoms. Asthma symptoms include chest tightness, difficulty breathing, and wheezing—a high pitched whistling sound you make when breathing. The thin layer of smooth muscle surrounding your airways react by tightening, further blocking airflow. Your mucus production increases and makes your breathing and coughing troubles even worse.
Sometimes the only symptom of asthma is a cough that won't go away. If your cough lasts six weeks or longer you may have cough-variant asthma. With cough-variant asthma, you generally don't have other typical asthma symptoms, such as shortness of breath and wheezing.
Cough-variant asthma may:
increase at night and keep you from sleeping
worsen when you are exercising
worsen when you have a cold
worsen when you are exposed to dust, cold air, air pollution, or other asthma triggers
Many people with cough-variant asthma don't know they have asthma since coughing is the only symptom. If you have a cough that won't go away, you should see your doctor for an accurate diagnosis.
If your doctor diagnoses you with cough-variant asthma, treatment is generally the same as treatment for other types of asthma. These inhaled medications are available in rapid-acting, long-acting, and combination formulations. Your cough should get better gradually with the use of these common asthma medications:
Bronchodilators rapidly relieve coughing and other asthma symptoms, such as wheezing and shortness of breath. You generally take quick-relief medications by breathing them into your lungs with an inhaler. A commonly prescribed quick-relief medication is albuterol (ProAir, Proventil, Ventolin), a bronchodilator that relieves your cough by relaxing and opening your narrowed airways.
Inhaled corticosteroids (steroids) help relieve your cough by reducing airway inflammation.
Over-the-counter (OTC) cough syrups and medications will not help your cough caused by asthma. In fact, they can actually make your asthma symptoms worse. The best way to treat your cough is to follow your asthma treatment plan and check with your doctor before trying any OTC medications. With the right treatment, your asthma can be controlled and your cough relieved.