Nicotine - this is not carcinogenic. However, it is highly addictive. Smokers find it very hard to quit because they are hooked on the nicotine. Nicotine is an extremely fast-acting drug. It reaches the brain within 15 seconds of being inhaled. If cigarettes and other tobacco products had no nicotine, the number of people who smoke every day would drop drastically. Without nicotine, the tobacco industry would collapse. Nicotine is used as a highly controlled insecticide. Exposure to sufficient amounts can lead to vomiting, seizures, depression of the CNS (central nervous system), and growth retardation. It can also undermine a fetus' proper development.