Nicotine is the addictive substance present in tobacco vegetation. Benzoic acid is also naturally found in plants, and is used commercially in dyes, perfumes, insect repellants, and meals preservatives. Existing cell, animal, and medical studies suggest that glycerin and propylene glycol irritate the lining of the lungs. One small medical examine from 2018 that discovered that the compounds modified vapers’ sputum—the mucosal lining that covers the interior respiratory tract—to precise different immune proteins. Some of these protein adjustments have been linked to bronchial asthma. Sign up for our Health Tip of the Day publication, and obtain day by day suggestions that will help you live your healthiest life.