Balloon Flower (Platycodon grandiflorus) is primarily used in traditional medicine, especially in East Asian countries such as China, Korea, and Japan, for the treatment of respiratory conditions, including bronchitis. In Traditional Chinese Medicine (TCM), the root of Balloon Flower, known as Jie Geng, is considered to have properties that help "open up" the lungs, expel phlegm, and relieve coughs. Its inclusion in various herbal formulas for bronchitis and other lung-related ailments is well documented in historical texts and pharmacopeias.

Scientific evidence for Balloon Flower's effectiveness in treating bronchitis is limited but emerging. Some laboratory studies have shown that extracts of Balloon Flower root possess anti-inflammatory, expectorant, and immunomodulatory effects, which might be beneficial in respiratory tract infections. For example, certain saponins isolated from the root have demonstrated the ability to reduce airway inflammation and mucus production in animal models. However, high-quality human clinical trials are scarce, and there is insufficient robust evidence to fully validate its efficacy for bronchitis treatment by modern medical standards.

In summary, while the traditional use of Balloon Flower for bronchitis is well established, scientific validation is limited and the current evidence would be best described as preliminary or supportive rather than conclusive.