Covonia Original Bronchial Balsam is a medical treatment that is designed to treat the symptoms of a dry cough caused by a cold or bronchitis. This treatment contains two active ingredients that help to provide relief for dry cough: Dextromethorphan Menthol Dextromethorphan is a cough suppressant that relieves the effect of a cough and menthol is a soothing agent that provides a cooling effect by blocking the calcium current in the nerves that is responsible for detecting the body’s temperature.