Nicotine is the addictive substance found in tobacco plants. Benzoic acid is also naturally found in plants, and is used commercially in dyes, perfumes, insect repellants, and food preservatives. Existing cell, animal, and scientific research recommend that glycerin and propylene glycol irritate the liner of the lungs. One small clinical study from 2018 that discovered that the compounds modified vapers’ sputum—the mucosal lining that covers the inner respiratory tract—to precise completely different immune proteins. Some of those protein changes have been linked to bronchial asthma. Sign up for our Health Tip of the Day e-newsletter, and obtain every day suggestions that may allow you to reside your healthiest life.