What causes cancer?

The causes of many cancers are not yet known, but a number of cancers seem to be caused by our lifestyle habits or by substances in our environment that affect our bodies.

The major causes of cancer are thought to include smoking, too much sun exposure, our diet and chemicals.  Cancer causing substances are called carcinogens.

Cancer is not contagious.  It cannot be passed on to friends or relatives or anyone else in the way that a cold or flu can.

People who have a family history of some cancers, such as breast or bowel cancer, may have a higher risk of developing that cancer.  In a very small number of families a change in the gene that controls cell growth is passed on from one generation to the next.  Not all family members get this change, but those who do may have a higher than normal chance of developing cancer.