Tobacco

Tobacco is a plant whose leaves are dried and consumed for their nicotine content, primarily by smoking (cigarettes, cigars, pipes, hookah), by smokeless use (chewing tobacco, snus, dip), or via electronic nicotine delivery systems (e-cigarettes/vapes). Legal and heavily commercialized, it is nonetheless the single largest cause of preventable illness and death in the United States. Its harm comes not from acute intoxication but from the long-term consequences of chronic use and from nicotine's powerful hold on the user.

Nicotine, tobacco's main active compound, binds nicotinic acetylcholine receptors in the brain, triggering release of dopamine and other neurotransmitters that produce a brief sense of alertness, relaxation, and reward. This reward signaling drives one of the fastest and strongest dependence patterns of any drug. The health damage, however, comes largely from the thousands of other chemicals in tobacco smoke — including dozens of known carcinogens — and from combustion products, not from nicotine alone.

Nicotine produces a short-lived lift in mood, alertness, and concentration, plus reduced appetite, alongside increased heart rate and blood pressure. Tolerance and dependence develop quickly, so much of ongoing use is driven by relieving withdrawal (irritability, anxiety, cravings, difficulty concentrating) rather than positive effect. Smoke and aerosol also cause immediate airway irritation, coughing, and reduced lung function.

Tobacco is the deadliest substance in this library, but its harm works differently from most drugs here: not acute overdose, but cumulative disease. Smoking is a leading cause of lung cancer and is linked to cancers of the mouth, throat, esophagus, bladder, pancreas, and more; it drives heart disease, stroke, COPD and emphysema, and it damages nearly every organ system. In the US it accounts for hundreds of thousands of deaths a year — more than alcohol, illicit drugs, and firearms combined. Nicotine itself is intensely addictive, making cessation hard, and nicotine is also a poison: liquid nicotine (vape refills) can be fatal to children who swallow it, and high exposure causes nausea, vomiting, and, at extreme doses, seizures. Smokeless tobacco causes oral cancers and gum disease. Vaping is not harmless: while likely less dangerous than combustible cigarettes for adults who fully switch, it delivers highly addictive nicotine, has driven youth addiction, and has been linked to lung injury (notably from illicit THC vapes containing vitamin E acetate). Secondhand smoke harms non-users. If a child swallows liquid nicotine, or anyone has severe vomiting, seizures, or trouble breathing after a high nicotine exposure, call 911, and Poison Control at 1-800-222-1222 can advise. Quitting sharply reduces these risks over time; evidence-based cessation support exists. This page has not yet been medically reviewed.