Viral infections like a cold can cause inflammation of the airways of the lungs. This may cause a cough, especially with activity or laughing. If a virus were the cause none of the antibiotics your mom took would be
effectiveEffective strength cough syrup in getting rid of the infection. If bacteria were the cause then the antibiotics would have gotten rid of the infection.
After the cold is gone, it is possible for the inflammation to linger. This inflammation can last for several weeks. Sometimes this inflammation may linger for 3 to 6 months. Eventually the inflammation will go away, and then the coughing will stop. This is called reactive airways disease (RAD) and behaves a lot like asthma. On a simple breathing test, called spirometry, this may not show up. This inflammation often clears more quickly when it is treated with an inhaled steroid medicine, which is given to treat asthma. Your mom may get well again by using an inhaled steroid every day. Usually this medicine does not provide immediate relief of symptoms. It may need to be used every day for several weeks to months for it to help. Sometimes an oral steroid, like prednisone, is given for a short period of time instead of the inhaled steroid. Your mom’s doctor is the best judge of this.
With your mother’s history of breast cancer, followed by chemotherapy and radiation therapy she should have a thorough physical exam. This will require a chest x-ray, possibly a CT scan and quite possibly a bronchoscopy. It would be best to know that there is nothing other than RAD causing your mom’s cough so that she gets the most helpful treatment.