Without these symptoms, it is not as likely that your cough is caused by asthma. Still, it is possible for a persistent cough to be the only symptom from asthma. If your cough is not easily explained by another diagnosis, your doctor may test you for asthma with breathing tests called "spirometry." Your doctor may also choose to try out an inhaler that is used to treat asthma to see if this relieves your symptoms.
One important trigger of a persistent cough is acid reflux from the stomach (which is known as gastroesophageal reflux disease, or GERD).
Do you have a recurring sour taste in your mouth, or do you frequently notice burning pain (called heartburn) behind your breastbone (sternum)?