Nicotine is the addictive substance present in tobacco crops. Benzoic acid is also naturally present in crops, and is used commercially in dyes, perfumes, insect repellants, and meals preservatives. Existing cell, animal, and clinical studies suggest that glycerin and propylene glycol irritate the lining of the lungs. One small clinical examine from 2018 that discovered that the compounds changed vapers’ sputum—the mucosal lining that covers the interior respiratory tract—to precise totally different immune proteins. Some of these protein modifications have been linked to asthma. Sign up for our Health Tip of the Day e-newsletter, and receive daily tips that may allow you to stay your healthiest life.