For coughs caused by a cold, the Committee on Herbal Medicinal Products HMPC mainly recommends saponin drugs and essential oil drugs./ Photo: Getty Images/Mladen ZivkovicWhile mucous drugs are the most common in dry coughs, saponin drugs such as primrose or liquorice root and essential oil drugs are recommended as expectorants for cold-related coughs (Table 1).For all drugs and their preparations, there is a lack of safety data on use in pregnant and breastfeeding women and use is therefore not recommended.In addition, a doctor should be consulted if symptoms persist for more than a week or worsen during treatment, or if dyspnea, fever or purulent sputum occur.Patients with gastritis or stomach ulcers should use the saponin-rich cowslip flowers and primrose root with caution.Overdose can cause stomach upset, vomiting, and diarrhea.Patients with active stomach ulcers, gallstones and other gallbladder problems should also be advised of horehound herb and peppermint or eucalyptus oil to consult a doctor before using the corresponding preparations or to refrain from using them.Patients with heartburn or diaphragmatic hernia may experience worsening of symptoms after ingestion of peppermint oil and treatment should be discontinued.Stomach complaints can also occur after taking thyme preparations and a slightly laxative effect can be observed with angel sweet rhizome.Sensitive individuals are sometimes allergic to cowslip blossoms, thyme oil, bitter and sweet fennel, or peppermint oil.Thyme oil, peppermint oil , eucalyptus oil and eucalyptus leaves are contraindicated for children under 2.5 years old because the essential oils can provoke laryngeal spasm.Bitter fennel oil and aniseed oil should only be used in adults over the age of 18 because of the estragole they contain, which has been shown to have a carcinogenic effect on mice.In the case of bitter fennel oil, it should also be noted that an overdose can impair the effectiveness of oral contraception and hormone replacement therapy due to its estrogenic activity.Inhalation and also oral ingestion of large amounts of menthol in peppermint oil or 1,8-cineol in eucalyptus oil can lead to dizziness, confusion, epileptic seizures, muscle weakness and double vision and severe gastrointestinal symptoms, diarrhea, rectal ulceration, apnea, nausea and cardiac arrhythmia cause.Eye contact with unwashed hands after applying essential oils may cause eye irritation.In addition, the essential oils should not be applied to injured or irritated skin.Full baths with essential oil drugs are contraindicated for large skin injuries and open wounds, acute skin diseases, high fever, severe infections, severe circulatory disorders and heart failure.Patients taking licorice-containing medications should not consume other licorice-containing products because of the potential for serious adverse events such as water retention, hypokalemia, hypertension, and cardiac arrhythmia.In addition, the concomitant use of diuretics, cardio-active steroid glycosides, corticosteroids, stimulant laxatives, or other drugs that may aggravate electrolyte imbalance is not recommended.Symptoms such as water retention, hypokalemia, hypertension, cardiac arrhythmia, and hypertensive encephalopathy have been reported with overdose and prolonged use (more than four weeks).Tables 3 to 6 contain a selection of preparations that are available on the German market (according to the ABDA article master).They are often approved or licensed or registered with the BfArM independently of the HMPC monograph.