Sunburn explainer

You’ve probably heard it said that the main cause of melanomas is too much sun exposure and many of us are familiar with the painful red skin, blisters and peeling that follow too much time in the sun. But what actually happens in the skin during a sunburn?

Sunburn is a radiation burn, caused when the ultraviolet (UV) rays of sunlight discharge too much energy into skin and damage DNA in the upper layer of skin cells. When absorbed by DNA, the extra energy causes some of the DNA chain to link up incorrectly. This interferes with accurate DNA copying, so cells start repairs to try to fix the mistakes. Too many DNA errors cause it to begin to self-destruct, to remove cells that can’t be safely replicated, and a day out in the sun can cause up to 100,000 DNA defects in each exposed skin cell.

Once skin cells detect high levels of DNA damage in themselves, they begin sending signals to attract immune cells into the skin. The skin’s blood vessels begin to leak into the spaces between skin cells to allow immune cells to ooze in, then destroy and then clean up unsafe cells. This extra fluid causes swelling and leads to red skin, a hot feeling and painful sensitivity. Immune cells start invading your skin while you’re still out in the sun and peaks 24 to 48 hours later, which is why the redness and painfulness of a sunburn can keep developing for a couple of days. Blisters form where whole layers of cells have been killed. The dead starts to detach from the layers underneath, and the space fills up with the fluid that has leaked into the skin.

Once the cell destruction and clean up process is complete, the lower layer of skin cells begins to grow quickly to replace them. Large sheets of dead cells are shed from the upper layer of the skin to make way for new growth, causing peeling; a sign that your sunburn is nearly healed. DNA damage also causes the cells that produce melanin (the pigment that gives our hair and skin its colour) to get to work, causing you to tan. The melanin is parcelled up and laid over the skin cells’ nuclei to shield the DNA inside from future UV exposure. But don’t rely on your tan to fully protect you next time – it’s only as good as SPF2 sunscreen. Premature ageing is another effect of too much UV exposure. Deeper in the skin, the excess energy causes reactive oxygen particles that damage many skin structures and ultimately cause deep wrinkling, a leathery appearance, darkened or yellowed skin tone, and dark blotches.

You can’t speed up sunburn healing, but in the meantime, you can relieve the discomfort by staying out of the sun, applying a cool compress, taking over-the-counter pain relievers, drinking plenty of water. If your pain is too severe to be managed by these measures, or there is extensive blistering, nausea, fever or dizziness, you should visit your doctor.

iToBoS aims to detect melanomas early and easily, but prevention is always better than cure. Excess UV exposure contributes to up to 95% of melanomas and 99% of non-melanoma skin cancers. Avoid repeating your sunburn by using sun protection whenever the UV index reaches 3 or higher, or you’re going to be outside for a long time.

This article has been writen by researchers of the University of Queensland. Please, take care and keep these important tips in mind!