Nicotine is the addictive substance found in tobacco vegetation. Benzoic acid is also naturally found in crops, and is used commercially in dyes, perfumes, insect repellants, and food preservatives. Existing cell, animal, and medical research recommend that glycerin and propylene glycol irritate the liner of the lungs. One small medical research from 2018 that found that the compounds changed vapers’ sputum—the mucosal lining that covers the inner respiratory tract—to express completely different immune proteins. Some of those protein changes have been linked to asthma. Sign up for our Health Tip of the Day newsletter, and obtain day by day suggestions that can assist you to reside your healthiest life.