Pepsin levels in bronchial lavage were higher in the ILD and chronic cough groups. This suggests that reflux may be involved in the etiology of chronic cough and ILD. Low pepsin values in patients receiving anti-reflux therapy have shown that occult reflux may occur. In our study, the high level of pepsin in bronchial lavage, especially in the chronic cough and ILD group, may be instructive in the etiology and treatment planning of the disease.