Effect of add-on therapy with leukotriene receptor antagonists and Chungsangboha-tang in patients with asthma: a protocol for a randomized, placebo-controlled, parallel, multicenter trial.

Background: Asthma is a chronic disease characterized by airway inflammation and obstruction. Treatment aims to control symptoms with minimal medication, using disease-controlling and symptom-relieving drugs. Inhaled steroids and beta2 agonists are common treatments; however, their long-term use can cause side effects.