Nicotine is the addictive substance found in tobacco vegetation. Benzoic acid can also be naturally present in crops, and is used commercially in dyes, perfumes, insect repellants, and food preservatives. Existing cell, animal, and medical studies counsel that glycerin and propylene glycol irritate the liner of the lungs. One small clinical examine from 2018 that found that the compounds modified vapers’ sputum—the mucosal lining that covers the interior respiratory tract—to express totally different immune proteins. Some of those protein adjustments have been linked to asthma. Sign up for our Health Tip of the Day newsletter, and obtain every day suggestions that can help you stay your healthiest life.