Nicotine is the addictive substance present in tobacco vegetation. Benzoic acid can be naturally present in crops, and is used commercially in dyes, perfumes, insect repellants, and meals preservatives. Existing cell, animal, and clinical studies counsel that glycerin and propylene glycol irritate the lining 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 specific totally different immune proteins. Some of these protein modifications have been linked to asthma. Sign up for our Health Tip of the Day newsletter, and receive daily tips that may assist you to stay your healthiest life.