Nicotine is the substance in tobacco (present in cigarettes, cigars, and pipe and chewing tobacco) that users become dependent on. It is also the active ingredient in some drug products used to help people quit smoking.
Most nicotine exposure is from smoking tobacco, although children may accidentally eat it (usually cigarettes or butts left in ashtrays or sometimes nicotine gum or patches), and some people use smokeless tobacco. Nearly all smokers smoke cigarettes, only a few percent smoke cigars or pipes.
In the United States, about 45 million adults (20% of all adults) smoke. About one half of current smokers will die prematurely of a disorder caused by smoking. Smoking is so deadly because smokers inhale hundreds of other substances, including ones that can cause cancer. However, all tobacco products contain toxins and possible carcinogens. Even smokeless tobacco products are not safe alternatives to smoking. Smoking is also the most common cause of unintentional home fires in the United States. Smoking-related fires kill more than 350 people and injure more than 900 each year.
Nicotine, when obtained through smoking, often has few obvious effects, although some people notice increased energy and ability to concentrate and decreased appetite. People not used to nicotine may have nausea, flushing, or both.
People who handle large amounts of tobacco leaves may absorb nicotine through their skin and develop nausea, vomiting, diarrhea, sweating, and weakness. This illness has been termed green tobacco sickness. Children who eat tobacco products can develop similar symptoms, along with agitation and confusion, sometimes from as little as one cigarette. However, serious or fatal toxicity in children is uncommon, in part because the vomiting empties the stomach.
Because smoking involves inhaling many harmful substances, it has many serious consequences. It harms nearly every organ in the body. The leading smoking-related health problems are the following:
Smoking also increases the risk of stroke, other cancers (such as bladder, esophageal, kidney, throat, and stomach), pneumonia and other respiratory infections, asthma, osteoporosis, periodontitis (gum disease), peptic ulcer disease, and cataracts. In all, smoking-related disorders account for about 435,000 deaths per year, or about 20% of all deaths. On average, smokers lose 10 to 14 years of life (7 minutes per cigarette).
People who do not smoke but who are exposed to smoke from others (passive, or secondhand smoking) can develop many of the same disorders as smokers, although the risks are lower. Smoking during pregnancy can cause problems such as preterm birth, a low birth weight, sudden infant death syndrome, and respiratory disorders such as childhood asthma. Children exposed to cigarette smoke lose more school days because of illness than nonexposed children.
The toxicity of smokeless tobacco can vary from one brand to another. Risks include heart and blood vessel disorders, mouth disorders (for example, cancers, gum recession, gingivitis, and periodontal disease and its consequences), and tumors.
Nicotine can interact with many drugs. Smoking also dries and wrinkles a person's skin, thins the hair, and turns the teeth yellow. Smokers tend to weigh about 10 pounds less than they would if they did not smoke.
Nicotine withdrawal (see Withdrawal) may result in many unpleasant symptoms, including a craving for nicotine, irritability, anxiety, poor concentration, restlessness, trembling (tremor), depression, headaches, drowsiness, and stomach upset. Many people gain weight while trying to stop smoking. Withdrawal is most troublesome in severely dependent people.
Doctors try to ask all their patients whether they smoke and, if so, how much. This lets them explain the risks to people and then begin discussion of quitting smoking. Testing is unnecessary. Motivated smokers should ask about ways to quit.
Nicotine poisoning can be overlooked. For example, children may swallow cigarettes or nicotine gum without being seen. Even when observed with tobacco in their mouth, it can be difficult to tell how much children have actually swallowed. People with green tobacco sickness may not connect their symptoms with handling tobacco.
Emergency treatment is rarely required except for children who have eaten products that contain nicotine. Doctors usually give activated charcoal by mouth to absorb any drug remaining in the gastrointestinal tract. Children who are very agitated may be given a sedative such as lorazepam.
Most issues regarding nicotine use involve efforts to quit smoking (see Smoking Cessation).
Last full review/revision May 2013 by Douglas E. Jorenby, PhD