Nicotine. Bottle of nicotine used for forensic research. Nicotine is a toxic drug found in small quantities in cigarettes. Larger doses will cause convulsions, paralysis of the brain, and death by paralysis of the respiratory system. Amounts over 40 milligrams (mg) can cause death. It is toxic if swallowed, and extremely toxic through skin contact. Forensic analysis is used to determine whether a particular case of poisoning involves nicotine. Tests such as spectroscopic analyses require a sample of pure nicotine to compare with the suspected poison. Sources of poisoning include cigarettes and nicotine medication to aid quitting smoking, especially if ingested by children.