Tobacco smoke contains nicotine which is highly addictive. Addiction experts have stated that nicotine is as addictive as cocaine and more addictive than heroin.

As well as nicotine, each cigarette contains more than 4,000 different chemicals many of which are toxic, and more than 50 of them cause cancer.

The details below explain some of the toxins found in tobacco smoke, and the way they harm the body.

Nicotine - When you smoke a cigarette nicotine affects your brain within seconds of inhaling. It increases your heart rate and causes a surge in the hormones in your brain. Nicotine can have a positive effect on your mood and your ability to concentrate. In between cigarettes, the levels of these hormones drop leaving you feeling irritable, anxious and in need of another cigarette.

As well as being addictive nicotine can be dangerous if you have high blood pressure. It increases the risk of accelerated hypertension, which is a sudden rise in already-high blood pressure that can cause headaches, blurred vision and vomiting. 

Nicotine also slows down your body's ability to heal itself by making your skin dehydrated.

However, nicotine is by no means the most dangerous substance in cigarettes. Substances much more dangerous found in cigarettes include: 

Tar - every breath of tobacco smoke deposits tar in your lungs. The tar in cigarette smoke contains chemicals which encourages the development of cancer cells in your body.

Carbon monoxide - When it is inhaled the poisonous gas carbon monoxide binds itself to the haemoglobin in your bloodstream and prevents it from carrying enough oxygen around your body. This is particularly dangerous for pregnant women, because it causes a severe lack of oxygen in an unborn baby.

Oxidant gases - Oxidant gases are gases that react with oxygen. They make your blood more likely to clot, which increases your risk of having a heart attack or stroke.

Benzene - Benzene is a chemical that used to be added to petrol. Exposure to benzene can cause cell damage and has been linked to a range of different cancers, such as leukemia and kidney cancer.

Polonium - Polonium is a highly radioactive substance and even tiny amounts can cause extensive damage to human tissue.

In addition to all of the above, other poisonous substances found in tobacco smoke include ammonia, hydrogen cyanide, mercury, arsenic, nickel, lead, formaldehyde and acetone. 

Risks to others

When you smoke, it is not just your health that is at risk, but the health of anyone who breathes in cigarette smoke (including those around you). The smoker only inhales about 15% of the smoke from a cigarette. The other 85% is absorbed into the atmosphere or inhaled by other people.

Breathing in this secondary smoke is known as passive, or secondary smoking. Passive smokers also have an increased risk of smoking-related diseases, particularly lung cancer and heart disease.

Non-smokers who share their house with a smoking partner are more likely to develop lung cancer than non-smokers who live with a non-smoking partner.

Risks to children

Children are at particular risk from the effects of passive smoking because they have an increased risk of developing chest infections during their first five years. Also, they are even more sensitive to smoke than adults because their bodies are young and still developing. 

Medical research shows that babies and children exposed to a smoky atmosphere are likely to have increased risk of lower respiratory tract infections (bronchitis, pneumonia), reduced lung function, asthma, sudden infant death, 'Glue ear' (which can lead to partial deafness).

Risks during pregnancy

Smoking can make you less fertile. Therefore, not smoking can improve your chances of conceiving.

If you smoke, there is a greater chance of complications occurring during pregnancy and labour such as sickness, miscarriage and bleeding. Smoking while pregnant can also increase the risk of premature birth and stillbirth.

Smoking during pregnancy can also affect your developing baby. Your baby may have a lower birth weight, be weaker and grow more slowly throughout their childhood. Research suggests that children exposed to smoke in the womb may do less well at school.