Nicotine is the addictive substance found in tobacco plants. Benzoic acid can also be naturally present in crops, and is used commercially in dyes, perfumes, insect repellants, and meals preservatives. Existing cell, animal, and clinical research counsel that glycerin and propylene glycol irritate the liner of the lungs. One small scientific study from 2018 that discovered that the compounds modified vapers’ sputum—the mucosal lining that covers the inner respiratory tract—to specific totally different immune proteins. Some of those protein modifications have been linked to bronchial asthma. Sign up for our Health Tip of the Day newsletter, and receive daily ideas that will help you stay your healthiest life.