Dry cough that continue after other cold symptoms clear or that occur without other symptoms may be caused by a variety of health problems. Some people start coughing when they breathe very dry, heated air. This can be caused by environmental irritation or Allergies.  This type of cough may be more noticeable when you first turn on your furnace in the fall, because dust and other irritants that have collected over the summer are blown into the air. Chronic dry cough are usually caused by irritation from cigarette smoke, environmental irritants, Allergies, postnasal drip or asthma. Several chronic lung diseases also cause a dry, hacking cough.