When we quit smoking, the first thing, essentially to start repairing itself, is the respiratory tract......and as soon as we take the last puff, the cilia start to regenerate themselves. In some people these cilia grow back faster than others. Coughing is a natural byproduct of the reemerging cilia.hen we quit smoking, the first thing, essentially to start repairing itself, is the respiratory tract......and as soon as we take the last puff, the cilia start to regenerate themselves. In some people these cilia grow back faster than others. Coughing is a natural byproduct of the reemerging cilia.