Terpenoids, a large and diverse class of naturally occurring organic chemicals derived from terpenes, have been widely studied for their pharmacological properties, including their effects on respiratory conditions such as dry cough. Several terpenoids, most notably menthol (found in mint oils) and cineole (eucalyptol, found in eucalyptus oil), have demonstrated antitussive (cough-suppressing) effects in both preclinical and clinical studies. Mechanistically, these compounds are thought to exert their effects by acting on airway sensory nerves, reducing irritation and suppressing the cough reflex. For example, menthol can activate cold-sensitive TRPM8 receptors, which may produce a cooling sensation and reduce the urge to cough.

Clinical evidence supports the use of certain terpenoid-containing remedies for symptomatic relief of dry cough. Over-the-counter cough syrups and lozenges often contain menthol or eucalyptus oil, and several double-blind, placebo-controlled trials have shown modest benefits in reducing cough frequency and severity. However, the level of evidence is moderate (rated 3/5) due to variability in study design, sample size, and the specific terpenoid used. It is important to note that while some terpenoids have demonstrated efficacy, the term "terpenoids" covers a wide range of compounds, not all of which have been studied for this indication.

In summary, there is scientific support, particularly for specific terpenoids such as menthol and cineole, in the management of dry cough, though the overall evidence base is moderate and further research is warranted.