Nicotine is the addictive substance found in tobacco vegetation. Benzoic acid is also naturally found in vegetation, and is used commercially in dyes, perfumes, insect repellants, and meals preservatives. Existing cell, animal, and medical studies recommend that glycerin and propylene glycol irritate the lining of the lungs. One small scientific research from 2018 that discovered that the compounds modified vapers’ sputum—the mucosal lining that covers the inner respiratory tract—to express different immune proteins. Some of these protein modifications have been linked to bronchial asthma. Sign up for our Health Tip of the Day publication, and obtain every day suggestions that may allow you to stay your healthiest life.