We’ve all had it before – the crusty, red spot on your face that just won’t go away.

Face creams won’t work. It can’t be popped no matter how hard you squeeze. Washing your skin makes no difference.

It can be embarrassing, annoying even, but we rarely think of these blemishes as dangerous. But what if I told you there was a chance this stubborn, red mark could be cancerous?

As a GP who has had her own brush with cancer, I’m concerned that many patients are unaware of the signs of the most common form of skin cancer.

And with the record-breaking hot weather this summer, cases are only going to rise, as the disease is strongly linked to sun exposure.

Thankfully, there are a few simple tricks that patients can learn that will help them tell the difference between a stubborn spot and cancer.

First though, it’s important to explain the different types of skin cancer, as this determines the symptoms – and the treatment.

Perhaps the most well-known form of the disease is also the most deadly: melanoma.

Around 20,000 people develop melanoma every year – and around 2,600 die as a result over the same time period.

Melanoma almost always appears in the same way: a mole that changes or grows.

This might mean that it gets larger, develops jagged edges or becomes asymmetrical. It might change colour – turning red, brown or black – or several colours at once. It might itch or bleed.

Time is of the essence with melanoma because it can spread throughout the body. However, the good news is that many people can recognise if a mole is changing, as long as they are looking.

Harder to spot are squamous cell carcinomas, a form of the disease that tends to appear as a small, red, crusty patch. Sometimes this mark can be painful. 

Crucially though, squamous cell carcinomas tend to grow quickly and spread around the body, meaning that – while less obvious than melanoma – this cancer is still often picked up by a watchful eye.

The same cannot be said for the most common form of skin cancer: basal cell carcinoma.

Basal cell carcinoma is very slow-growing, which is good news, but it is also the reason that people often miss it.

Instead, it typically shows up as a sore that bleeds, oozes or crusts and – this is the most important part – it doesn’t go away.

Sometimes basal cell carcinoma can be even more subtle than this and simply appear as a shiny bump or a scaly reddish patch.

I’ve seen cases before that have initially been mistaken for non-threatening skin conditions like eczema or psoriasis. I know patients who have described how their basal cell carcinoma was, at first, ‘that little spot that doesn’t go away'.

This cancer also tends to be more common on the ears, scalp, neck or face.

And while the disease is thankfully not as deadly as melanoma – in fact, there are fewer than 100 deaths every year in the UK – the longer patients delay in treating basal cell carcinoma, the harder it becomes to treat.

This is because the cancer burrows down into the skin. The deeper it gets, the more intensive the surgery will need to be.

Of course, the best way to tackle skin cancer in all its forms is to avoid getting it in the first place. This means protecting the skin from UV rays – the harmful radiation given off by the sun.

This seems simple enough but an astonishing number of Britons are failing to protect their skin.

A survey published earlier this year by charity Melanoma Focus revealed that one in nine British adults have deliberately burnt their skin – putting them at a heightened risk of skin cancer.

The survey of more than 3,000 adults in the UK found that an astonishing one in three adults also admitted to never using suncream.

The NHS advice is, when in the sun, always use suncream with an SPF of at least 30, applying six to eight teaspoons to the entire body every two hours – and always after swimming, sweating or towelling dry.

However, the most effective measure against the damages of direct sunlight is to stay out of it altogether by remaining in the shade when the sun is at its strongest – between 11am and 3pm.

All that said, basal cell carcinoma is treatable thanks to modern medicine – when caught early enough. There are now a number of effective treatments, including some as simple as prescription creams.

But the trick is to spot it in time. This means paying attention to marks that refuse to go away or spots that just won’t budge. If you think this describes your blemish, it might be time to talk to your GP.