Yes. Dr. Buteyko discovered that chronic over-breathing can be very dangerous or even lethal. In order to protect itself, the body creates various defense mechanisms to reduce hyperventilation. Coughing, wheezing, suffocation attacks, excessive mucus, and a stuffy nose are just a few of these mechanisms. The purpose of each of these symptoms is to reduce hyperventilation, thereby protecting the body from even greater harm. When a person reduces their hyperventilation voluntarily, these symptoms are no longer needed. Many people greatly reduce such symptoms within the first few weeks of beginning the Buteyko Breathing Normalization Method course. Ultimately, many people lose their symptoms completely.