There are 600 ingredients in a cigarette and can produce up to 7000 chemicals when burned. Nicotine is a drug that makes cigarettes addictive. One cigarette has a nicotine level of 8 to 20 milligrams. There are also harmful chemicals found in a cigarette such as carbon monoxide, nitrogen oxides, methane, acetone, phenols, and naphthalene which are all harmful to the body.