The terpenoids are responsible for the expectorant activity, while a variety of flavonoids are responsible for the spasmolytic effect of thyme on the bronchioles.

Recent studies have shown that whereas epithelial cells in the human respiratory tract express predominantly the [alpha]-2,6 sialic acid receptor, cells expressing the [alpha]-2,3 receptor were detected only occasionally in the upper respiratory tract; however, measurable expression of [alpha]-2,3-linked sialic acid receptors was found in some cells in the alveolar epithelium and at the junction of alveolus and terminal bronchiole (35).

This case illustrates the classic findings of carbon pigment deposition around terminal bronchioles, dust macules, and mixed dust fibrosis.