It's the chicken and the egg thing with acid reflux and asthma. 75% of people with asthma also have reflux. Acid coming up can irritate the lungs and cause an asthmatic reaction. All of the squeezing of the stomach that takes place with asthmatic coughing can result in more reflux. It can be a vicious cycle.
If you have both, the trick is to aggresively treat both and at the same time to get things back under control.