Sundew has a long history of use for treating coughs and has been shown in one study to have cough-relieving abilities.
A number of herbs have a rich history of use for treating coughs due to colds, bronchitis, or other mild conditions. Only a few studies have examined the effectiveness of these herbs. However, their effectiveness is well-known by practitioners of herbal medicine the world over. Among those herbs that have been shown to have some degree of cough-relieving activity are marshmallow,sundew, and coltsfoot. Use of coltsfoot should be limited to preparations of the leaves and flowers only, as the root is high in pyrrolizidine alkaloids, constituents that may be toxic to the liver.
Thyme has a long history of use in Europe for the treatment of dry, spasmodic coughs as well as for bronchitis. Many constituents in thyme team up to provide its antitussive (preventing and treating a cough), antispasmodic, and expectorant actions. The primary constituents are the volatile oils, which include the phenols thymol and carvacol. These are complemented by the actions of flavonoids along with saponins. Thyme, either alone or in combination with herbs such as sundew, continues to be one of the most commonly recommended herbs in Europe for the treatment of dry, spasmodic coughs as well as for whooping cough. Because of its apparent safety, it has become a favorite for treating coughs in small children.