Nicotine is the addictive substance present in tobacco crops. Benzoic acid can be naturally present in vegetation, and is used commercially in dyes, perfumes, insect repellants, and meals preservatives. Existing cell, animal, and clinical studies recommend that glycerin and propylene glycol irritate the liner of the lungs. One small clinical research from 2018 that discovered that the compounds modified vapers’ sputum—the mucosal lining that covers the inner respiratory tract—to express completely different immune proteins. Some of these protein changes have been linked to bronchial asthma. Sign up for our Health Tip of the Day newsletter, and obtain daily tips that will allow you to live your healthiest life.