Certain things are added to tobacco for technical, taste-related and sales reasons. For example, in order to avoid the tobacco crumbling, an absorbent substance, such as glycerol, is added. Various salts are added to give the cigarette an even-burning quality. Some additives are used in the paper. Flavourings are used to give a brand of cigarette a particular taste. These include cocoa, liquorice and sugar.

Menthol and eugenol (aroma of cloves) are added to act as a pain reducer on the mucous membranes of the throat. This reduces the irritation caused by cigarette smoke.

The tobacco industry has also been accused of adding ammonia to cigarettes to increase the addiction to nicotine. Ammonia works by increasing the nicotine vapour in the cigarette, giving the smoker a bigger ‘kick’. This accusation has caused controversy, as ammonia is naturally present in varying degrees, in different tobaccos. In addition, ammonia is also a by-product when the cigarette is smoked.

Some of these additives appear harmless in their natural form, but may be toxic in combination with other substances. When additives are burned, new products of combustion are formed, and these may be toxic.