It starts with a tiny black dot on your phone screen.

Then, before you know it, your device is down with a bad case of ‘pixel cancer’.

Fast-spreading and incurable, it occurs when pixels on a digital display ‘die’ due to physical damage and it can make parts of the screen completely unusable.

“Your phone has well over a million pixels on the screen, each pixel is used to display a colour and together they make the picture we see,” Long he said.

“If a pixel loses its connection to power or for some reason just fails, it will be ‘off’ permanently.”

A dead pixel will no longer display colour or respond to touch, so a large cluster of dead pixels can make parts of a touch screen unresponsive.

“What actually causes that to happen is tough to say, but in most cases it’s physical damage,” Long said.

When a single pixel fails on its own, it’s unlikely the damage will spread.

But when the problem is caused by phsyical damage to the screen, the risk of it spreading to other pixels (so-called ‘pixel cancer’) skyrockets.

And your chances of being able to fix the dead pixels plummet.

“Sadly, it’s unlikely you can fix the actual issue but it’s only the screen that has damage, so you don’t need a whole new phone,” Long said.

“A new screen on an older phone is far cheaper than almost any new phone, and a new screen on a more recent phone, while likely expensive, is still far cheaper than buying the same phone again.”

Common causes of ‘pixel cancer’ include direct physical damage to the front of the screen or bumps to the edge of the screen at the wrong place or on the wrong angle.

Long recommends investing in a high quality protective phone case to prevent physical damage.

He also said it’s a good idea to update your case from time to time, as they can become soft over time and offer less protection.

“Also, don’t drop or bump your phone – it’s worth a lot of money.”