Nicotine is the addictive substance found 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 clinical research recommend that glycerin and propylene glycol irritate the liner of the lungs. One small medical study from 2018 that found that the compounds changed vapers’ sputum—the mucosal lining that covers the inner respiratory tract—to precise totally different immune proteins. Some of those protein adjustments have been linked to bronchial asthma. Sign up for our Health Tip of the Day e-newsletter, and receive daily ideas that can assist you to live your healthiest life.