Nicotine is the addictive substance present in tobacco plants. Benzoic acid is also naturally present in vegetation, 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 medical study from 2018 that found that the compounds changed vapers’ sputum—the mucosal lining that covers the inner respiratory tract—to express completely different immune proteins. Some of these protein modifications have been linked to bronchial asthma. Sign up for our Health Tip of the Day newsletter, and obtain every day tips that may assist you to stay your healthiest life.