Moles changing on the skin could be a sign of skin cancer - which kills more than 2,000 people in the UK every year.
It can difficult to know exactly what to look out for because many marks on the skin are completely harmless.
But cancerous moles - melanoma - can spread to other areas of the body and can be extremely dangerous.
They are often caused by too much sun exposure, stressed a GP as temperatures are expected to rocket to the mid 30s again next month.
"Melanoma is a type of skin cancer that is caused by UV light," Dr Dominic Greenyer, from The Health Suite, said.
"Spending prolonged periods of time in the sun or using sunbeds regularly can increase your chances of this cancer developing.
"If left untreated, melanoma can spread to other areas of the body and can be extremely dangerous.
"There are a few changes in moles to look out for which can allow you to detect the signs of melanoma early and seek treatment."
The first thing to look out for is any alterations in the colour of moles.
Dr Greenyer said: "Normal moles can range in colour but are usually the same solid colour.
"Whereas melanomas can be a combination of more than one or two - such as brown mixed with a black, red, pink, white or blue tint."
Almost nine in ten (87.4 per cent) people diagnosed with melanoma skin cancer in England survive their disease for ten years or more, it is predicted.
Melanoma skin cancer ten-year survival in England is higher in females than males.
But if a mole has changed in shape, then this is also something to consider speaking to your doctor about.
"Most melanomas are likely to be uneven or irregular in shape," the GP added.
"Whereas ordinary moles are usually more even and both halves look mostly the same.
"The borders of a melanoma tend to be uneven, irregular or jagged - differing from normal moles which are uniform and round."
The Health Suite also recommends paying attention to the size of any moles and monitoring whether they are growing wider.
Melanomas tend to be significantly bigger than normal moles - 6mm versus the size of the flat end of a pencil or smaller.
Other things to keep an eye on include moles that are:
- Swollen or sore
- Inflamed
- Bleeding
- Itchy
- Crusty
The NHS states there is no safe or healthy way to get a tan, and great care should be taken when in the sun.
This includes spending time in the shade when the sun is strongest and covering up with suitable clothing.
