Almost everybody has moles. They are more common in pale-skinned people – such as European caucasians – but all races can have them. Some are present at birth, but most come on during childhood or adolescence.

In their teenage years up to early adulthood, it is perfectly normal for people to develop further moles. Even if you develop a new one after the age of 15, it is unlikely to be something to worry about. But according to David Gawkrodger, professor of Dermatology at Sheffield University, it's a good idea to spend a few minutes checking any newly appearing mole. The things to look out for are: if the mole rapidly enlarges, changes in colour (ie it becomes darker or lighter or goes red), if it is irregular in outline, if it starts to itch – and certainly if it starts to bleed or ulcerate. If any of these changes occur, seek medical attention immediately.

A good tip to monitor moles is to use old photographs: sometimes people think a mole has suddenly appeared when it's been present for years. If you do see a change, ask your doctor to refer you to a dermatologist who will place a dermascope over the mole to make any abnormalities visible.