Some natural cough syrups contain wild cherry bark, a natural remedy long used in herbal medicine. Extracted from the Prunus serotina tree, wild cherry bark is thought to suppress coughs and aid in the treatment of the common cold.
Despite its long history of use, few scientific studies have explored wild cherry bark and its possible health benefits. However, some research suggests that other natural substances may help alleviate coughs. For instance, there's some evidence that honey may help decrease the frequency and severity of coughs. In addition, marshmallow (an herb available in tea form) may possess cough-suppressing properties.