Nicotine is the addictive substance present in tobacco vegetation. Benzoic acid is also naturally present in plants, and is used commercially in dyes, perfumes, insect repellants, and meals preservatives. Existing cell, animal, and clinical research suggest that glycerin and propylene glycol irritate the lining of the lungs. One small medical study from 2018 that discovered that the compounds modified vapers’ sputum—the mucosal lining that covers the internal respiratory tract—to express 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 obtain every day suggestions that will help you reside your healthiest life.