Lactucarium, sometimes called "lettuce opium," is a milky fluid derived from wild lettuce (Lactuca virosa) and related species. Historically, it has been used in folk medicine for its mild sedative and analgesic effects. In the context of supporting the bronchial or respiratory system, lactucarium was occasionally employed in the 19th and early 20th centuries as a traditional remedy for coughs, asthma, and bronchitis, largely due to its reputed ability to calm irritation and produce mild sedation that might reduce coughing fits. However, these uses were based primarily on anecdotal reports and traditional herbal practices rather than scientific studies.

Modern scientific validation of lactucarium’s effects on the bronchial system is lacking. There are no well-designed clinical trials or pharmacological studies that demonstrate direct bronchodilatory, anti-inflammatory, or expectorant effects relevant to respiratory health. Most contemporary pharmacological interest in lactucarium focuses on its weak sedative properties, which are far less potent than pharmaceutical alternatives. As such, while lactucarium has a historical tradition of use for bronchial and respiratory complaints, this is not supported by robust scientific evidence.

In summary, the use of lactucarium to support the bronchial system is justified primarily by tradition, with very limited and low-quality evidence to support its efficacy in this area.