In a person who has a normal chest x-ray and who doesn’t smoke the most common causes of a chronic cough are asthma, chronic sinus problem, postnasal drip, and heartburn. A cough can also be a side effect of a group of medicines used to treat high blood pressure called angiotensin converting enzyme (ACE) inhibitors. Other possible causes are infection and irritation during the fall and winter months. Since it occurs during your worst allergy season, this suggests that allergy could be another possible cause. Also your ongoing cough could be due to a combination of these causes.
Viral infections like a cold can cause irritation of the airways of the lungs. This irritation can cause a dry hacking cough. After the cold is gone, it is possible for the irritation to linger. This irritation can last for several weeks. Sometimes this irritation may linger for 3 to 6 months. Eventually the irritation will go away, and then the coughing will stop. This is called reactive airways disease (RAD) and behaves a lot like asthma. This irritation often clears more quickly when it is treated with an inhaled steroid, which is used to treat asthma. Your doctor is the best judge of this.
When this continues, it is generally considered to be asthma. A lung problem such as asthma can cause a cough. A cough can be the only symptom of asthma. Testing can be helpful to show if your cough is due to asthma or RAD. Generally testing starts with a simple breathing test called spirometry. This test provides detailed information about how your lungs are working. It will show if there is obstruction in your airways.
To really test for asthma it is best to repeat this test after using a rescue inhaler, an inhaled bronchodilator. This measures how much the bronchodilator helps your lungs by reversing the problem. When there is a 20% increase, the test is positive for asthma.
There are a variety of things that can make asthma worse. These things are called triggers. Allergies, postnasal drip, and infections are common triggers of asthma. Also some people start to have problems with asthma only after having a severe respiratory infection. Once you have asthma, you will always have asthma. It does vary from person to person. For some people the symptoms will come and go. For others the symptoms are constant. There is no cure at this time, but it can be controlled with medicine.
Postnasal drip is drainage from the nose and sinuses dripping down the back of the throat. There could be several reasons for this drainage. One reason is an allergy. A second reason is a non-allergic, non-infectious inflammation in the sinuses that can linger after a cold. A third reason is chronic sinusitis. Postnasal drip can cause a dry hacking cough as a result of irritation of the throat and lungs. The fat content in dairy products can thicken mucus. Generally eating dairy products with less fat content is helpful. It sounds like you are drinking plenty of water. That will help to thin the mucus so that it moves more easily.
An antihistamine can dry up the postnasal drip. However, it may make the mucus thicker and more difficult to move. A decongestant like Sudafed® (pseudoephedrine) can thin the postnasal drip and decrease the swelling so it drains easier. A combination antihistamine-decongestant will do both. Check with your doctor to see what would help you more. Often an antihistamine and decongestant are taken only when the postnasal drip gets bad. It may be more helpful to take the antihistamine and decongestant on a regular basis.
A nasal wash helps remove mucus and germs from your nose and sinuses. This can temporarily decrease the postnasal drip and lessen your cough. A prescription nasal steroid spray, like Flonase® (fluticasone), decreases mucus production by decreasing the inflammation of the nose and sinuses. This may prevent the postnasal drip and coughing. To get the most help from a nasal steroid spray use it after doing a nasal wash. A nasal steroid spray does not provide immediate relief of symptoms. It may require several weeks of routine use to become effective. Sometimes it takes the antihistamine, the decongestant, and the nasal wash followed by the nasal steroid spray ALL used routinely to keep the postnasal drip from bothering you. Please read our Nasal Wash MedFact at http://www.nationaljewish.org/medfacts/nasal.html for more information about this technique. Share this information with your doctor to see if you would benefit from this daily treatment.
You will need to continue to work with your doctor to find out the nature of the problem that is causing your dry hacking cough. An allergist would be the type of specialist to identify if this is due to allergies and the best treatment. An ENT would be the type of specialist to identify a sinus problem and the best treatment. A gastroenterologist is the type of specialist to let you know if heartburn is causing your symptoms and the best treatment. A pulmonologist would be the type of specialist to identify a lung problem and the best treatment.