Many Young Adults Who Began Vaping as Teens Can't Shake the Habit KFF Health News If you don't vape, don't start. Most e cigarettes contain nicotine, which is highly addictive and harmful to your health, especially for teens, young adults and those who are pregnant. Learn more about Oral Health Risks of Vaping Dangers of vapes and e cigs to oral health Insights Teens say they don't vape, they 'Juul.' That makes the activity hard to track Los Angeles Times