Malabar nut (Justicia adhatoda or Adhatoda vasica) has a long history of use in traditional Ayurvedic and Unani medicine for respiratory complaints, including dry cough. The primary active compound, vasicine, and its related alkaloids are well-documented for their bronchodilatory, expectorant, and antitussive (cough-suppressing) activities. Several preclinical studies have shown that extracts of Malabar nut can suppress cough reflex in animal models, reduce airway inflammation, and help liquefy and expel bronchial secretions. These effects are attributed to both the stimulation of respiratory tract secretions (making dry coughs more productive) and a direct soothing action on irritated airway mucosa.

Human clinical evidence, while less abundant, is growing. Some small clinical trials and observational studies have reported that formulations containing Malabar nut extract can reduce cough frequency and severity in patients with acute and chronic bronchitis, including those primarily experiencing dry cough. The World Health Organization and several national pharmacopoeias recognize Malabar nut as an ingredient in herbal cough remedies. However, most commercial cough syrups and polyherbal formulations use it in combination with other herbs, and high-quality randomized controlled trials in isolated dry cough populations are still limited.

In summary, Malabar nut's use in supporting or treating dry cough is backed by both traditional and scientific evidence, especially from preclinical and some early clinical studies, justifying its inclusion in cough remedies. Ongoing research continues to clarify its mechanisms and potential in human populations.