Tobacco is name for the dried leaves of the tobacco plant, which include the highly addictive active ingredient nicotine. Tobacco is most commonly smoked, either in the form of a cigarette, cigar, or in a pipe. Snuff is a form of tobacco that is sniffed up the nose.

Up until the 1960s, it was believed that smoking tobacco was good for your health, but after it became public knowledge that smoking can cause cancer, people in most developed countries started to kick the habit and the number of smokers started to decline. 

In the UK about 30% of the population are smokers, who contribute almost £10 billion every year to the government in excise duty on tobacco and cigarettes.

The main active ingredient of tobacco is nicotine, which is a very fast-acting stimulant that increases blood pressure and pulse rate, and first-time users can experience dizziness and nausea. The general effects of smoking tobacco differ in individuals, but regular smokers often find that it helps to relax them, combat stress, alleviate anxiety, suppress boredom and help concentration.

Tobacco smoke, which is inhaled into the lungs, contains more than just nicotine. The list of government permitted addictives includes acetone, used to make paint stripper; ammonia, contained in toilet cleaners; butane, a form of lighter fuel; and beta-naphthyl methylether, more commonly known as mothballs. Smokers also take the risk of inhaling hydrogen cyanide, the poison used in gas chambers; methanol, a rocket fuel; arsenic; and carbon monoxide, the poisonous gas in car exhausts. Other ingredients found in tobacco products include cocoa, sugars and dried fruit extracts that are used to enhance the taste.

Nicotine is an extremely addictive chemical, and users soon build up a tolerance and run the risk of becoming chain smokers. Regular smoking greatly increases the chances of developing serious illness, such as cancers, heart disease and bronchitis. Smokers can also suffer from bad breath, nicotine staining on the teeth and fingers and coughs and chest complaints. Smoking results in the premature death of over 100,000 people in the UK every year.

There is also a risk to non-smokers though breathing in secondary smoke, known as passive smoking.