The average adult has between 10 and 40 moles, whether they are perfectly placed beauty spots, or unloved hairy blemishes. Because of their association with skin cancer, moles are often seen as a direct result of sun exposure but, while it is thought that UV light can contribute to moles forming, it isn’t unusual to be born with them.

What exactly are moles?

Moles (scientific term: melanocytic naevi) are clusters of pigment-producing cells called melanocytes. These splodges can vary massively in size and appearance – bumpy, smooth, flat, protruding or hairy – but they usually have neat edges and are round or oval. The melanin the cells produce means that moles are usually browner than the rest of the skin, although they can also be skin-coloured. Rarer moles, called halo naevi, are surrounded by a white ring, where the skin has lost its melanin, while blue naevi look dark blue, on account of the melanocytes being deep within the skin.

Why do we get moles?

Most moles appear in the first 30 years of life. They are more common, and prominent, in fair-skinned people, and a propensity for having moles can also run in families. Moles often appear and disappear according to hormonal changes. Pregnancy can make them darker, puberty can multiply them, and their numbers are likely to diminish in old age. However, moles always stay for years, unlike freckles, which tend to be smaller and paler and can temporarily pop out after sun exposure.

Should I worry if my mole changes in appearance?

It isn’t uncommon for moles to morph over time. Sun exposure and hormones can make them darker, or they can become raised, and flatten again, or grow paler. It is when a mole changes quickly that it is worth getting it seen by a doctor. Look out for rapid changes in shape, fuzzy edges developing, growing larger or bleeding easily.

What do cancerous moles look like?

Most moles have only one or two colours, whereas cancerous moles – melanomas – can be an uneven mixture of light brown, dark brown, black, red or pink. Ragged edges, very large moles and bleeding, itching, swollen, crusty or inflamed moles all warrant a visit to the GP. If you check your moles every few months, you should notice anything worth reporting, but even if you think a mole warrants medical assessment, don’t panic: atypical moles affect 10% of the population but only one in 10,000 of these people will have a melanoma. However, it’s best to be on the safe side, because melanoma can be life-threatening.

What exactly is melanoma?

It’s the most aggressive form of skin cancer, because it can spread to other organs in the body. In England and Wales, 90% of people who are treated for melanoma will survive for 10 years after being diagnosed. But while the overall outlook is good, it depends on what stage the cancer has reached when it is detected, and therefore whether it has had time to spread. Non-melanoma skin cancer is far more common, but rarely spreads. It usually presents itself as a hard red lump, or a flat scaly patch that doesn’t heal within a few weeks.

What happens if the doctor has concerns about my mole?

You should be referred to a skin specialist within a few weeks, who will examine the mole, and check your skin for other moles. If they think you have melanoma, they will usually perform what is called an excision biopsy, which means they will remove the entire mole and a 2mm margin around it for good measure, and check afterwards whether it is malignant (cancerous). This minor surgery is done with a local anaesthetic, and the wound is stitched up afterwards.

How common is melanoma?

In 2013, there were 14,500 new cases of melanoma (and 72,100 new cases of non-melanoma skin cancer) in the UK. Melanoma is the fifth most common cancer in the UK. British skin cancer rates are more than four times higher than they were in the late 1970s in Great Britain: it is thought this is partly due to increased awareness leading to higher detection rates, and also because more of us take regular holidays in hot countries.

What causes melanoma?

Exposure to ultraviolet light increases the risk. Whether from sunshine or solariums, UVA and UVB rays penetrate deep into the skin and can damage its DNA, leading to cancer. You are more likely to get melanoma if you have lots of moles or freckles, pale skin that burns easily, red or blond hair, or a family member who has had the disease.

How can I prevent cancerous moles?

You don’t have to get sunburn to increase your risk of skin cancer. You might get it even if you don’t sunbathe – but the more time you spend in the sun, the higher the risk. If you have pale skin or lots of moles, it is even more important to avoid overexposure. Stay out of the midday sun, wear sunscreen and wide-brimmed hats, and don’t be tempted by sunbeds. Using a sunbed won’t prime your skin for safer sunbathing while on holiday; it will merely increase your exposure to UV light.

I don’t have skin cancer but I really hate how my mole looks

You are not alone. According to a survey of cosmetic surgeons last year, there was a 127% rise from the previous year in people asking about mole removal. But even if you can afford to pay a private surgeon, the decision shouldn’t be taken lightly, because the resulting scar could end up bothering you more than the mole did.