Nicotine is the addictive substance found in tobacco vegetation. Benzoic acid can be naturally present in vegetation, and is used commercially in dyes, perfumes, insect repellants, and meals preservatives. Existing cell, animal, and scientific research recommend that glycerin and propylene glycol irritate the lining of the lungs. One small scientific examine from 2018 that found that the compounds changed vapers’ sputum—the mucosal lining that covers the interior respiratory tract—to specific completely different immune proteins. Some of those protein changes have been linked to asthma. Sign up for our Health Tip of the Day publication, and obtain every day ideas that can allow you to stay your healthiest life.