The asthmatic who has been diagnosed has at least one prescribed medication to take to control his symptoms. Even so, he may cough and experience other symptoms. Usually, the coughing signals additional health issues — his asthma is worsening, it is poorly controlled or he has an upper respiratory infection.
He can find relief from the coughing with simple measures or the correct diagnosis and treatment.
The information in this article is intended to provide information. It is not intended as medical advice. If you have health concerns, please visit your doctor.
If you are using at least one inhaler to manage your asthma, you probably got instructions from your doctor about how to use it correctly to manage your condition. In case you begin coughing and can’t control it, asthma coughing relief is likely to be the only thing on your mind as you try to stop coughing.
Your asthma might not be as well controlled as it should be. If you are only using your inhaler as your doctor prescribed and it isn’t enough, you may need an additional long-acting inhaler or a nebulizer. Your doctor will discuss your coughing and any additional symptoms in detail with you. He may prescribe a long-acting inhaler such as Azmacort, Qvar, Aerobid or Flovent, according to Pat Bass, About guide. These inhalers contain a corticosteroid and should only be used twice a day, every day. The steroid in these inhalers controls lung and airway inflammation, helping to avoid asthma attacks — and coughing. If you have developed a chronic cough, call your doctor if it has been present for at least three weeks. If you cough at night and it keeps you up; experience significant pain as you cough; cough up blood; or pass out when you cough, contact your doctor immediately. 
If your cough is “productive,” that is, you bring up phlegm or mucous, drink more clear fluids. Add water, tea or clear lemon-lime soda to your daily liquid intake. Doing so helps your body to thin the mucous present in your lungs and throat, making it easier for you to actually expel it when you cough, states the University of Maryland Medical Center. 
Avoid Cigarettes and Smoke
Some asthmatics are allergic to cigarette smoke. If you are one, do everything you can to avoid secondhand smoke, which, in addition to making your condition worse, puts you at increased risk of developing lung cancer. If you have a relative or co-worker who smokes, try not to be around them as they smoke. If you smoke, stop. The smoke and irritants only make your condition worse. 
If your asthma symptoms are otherwise well-controlled, but you have a dry, tickly cough, sucking on cough lozenges or hard candy can help relieve the tickliness and dry throat, reports the University of Maryland Medical Center  If you opt for cough lozenges, follow the dosage instructions on the box.
If you have a small child under the age of three who has been diagnosed with asthma, do not give cough lozenges to him. The risk of choking is too high. 
Asthmatics with allergy-induced asthma develop periodic allergic irritation from the allergens surrounding them. If your asthma stems from allergies and you develop the typical runny and stuffy nose, a non-drowsy antihistamine can help you. If your coughing is caused by your allergies, these medications can give you asthma coughing relief as long as you take the correct medications and you take them according to your doctor’s orders. These medications include loratadine (Claritin), fexofenadine (Allegra, which, as of 2011, came out in an over-the-counter formulation) and cetirizine (Zyrtec). Claritin and Zyrtec are also available over-the-counter. 
References and Image Credit
 Cough. University of Maryland Medical Center. Retrieved at https://www.umm.edu/altmed/articles/cough-000042.htm
 Pat Bass. Is My Chronic Cough Related to My Asthma? About.com Asthma. November 2010. Retrieved at https://asthma.about.com/od/asthmabasics/a/basic_chroniccough.htm
Smoking Cigarette Credit Salvatore Vuono