Nicotine replacement therapy works by reducing cravings caused by nicotine addiction. Nicotine replacement therapy works by reducing cravings due to nicotine addiction. Nicotine in any form is contraindicated in individuals with a known hypersensitivity to nicotine. Smoking cigarettes can lead to nicotine addiction. Hookah smokers inhale nicotine, which is an addictive chemical. Tobacco contains the highly addictive stimulant alkaloid nicotine as well as harmala alkaloids. Examples of psychoactive substances include caffeine, alcohol, cocaine, LSD, nicotine and cannabis. Bupropion reduces the severity of nicotine cravings and withdrawal symptoms. The nicotine in tobacco can also be dangerous. They also reported suffering from Green tobacco sickness, a form of nicotine poisoning. Nicotinic receptors also respond to drugs such as the agonist nicotine. The pouches contain the addictive chemical nicotine. Studies have linked methylation of the "MAOA" gene with nicotine and alcohol dependence in women. Studies of orexin involvement in nicotine addiction have had mixed results. Other devices to deliver inhaled nicotine have been developed.