Nicotine is the addictive substance present in tobacco vegetation. Benzoic acid can also be naturally found in crops, and is used commercially in dyes, perfumes, insect repellants, and food preservatives. Existing cell, animal, and scientific studies counsel that glycerin and propylene glycol irritate the liner of the lungs. One small clinical examine from 2018 that discovered that the compounds changed vapers’ sputum—the mucosal lining that covers the inner respiratory tract—to specific different immune proteins. Some of these protein modifications have been linked to asthma. Sign up for our Health Tip of the Day e-newsletter, and receive daily suggestions that can allow you to reside your healthiest life.