Nicotine is the addictive substance found in tobacco vegetation. Benzoic acid is also naturally present in plants, and is used commercially in dyes, perfumes, insect repellants, and food preservatives. Existing cell, animal, and clinical research recommend that glycerin and propylene glycol irritate the liner of the lungs. One small medical research from 2018 that discovered that the compounds modified vapers’ sputum—the mucosal lining that covers the interior 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 tips that may help you stay your healthiest life.