Question: Why does our skin react to the sun and get burnt? And if so how does sun cream protect us?

Reka Nagy answered on 10 Nov 2016:

Sunburns are actually the result of a very complex process through which your body protects itself from getting skin cancer.

Here’s how this happens:

Ultraviolet rays coming from the sun can damage our skin, breaking the DNA inside them. When this happens, the cells signal to our body that something is going wrong, and our bodies respond by producing more melanin – that’s a brown coloured substance produced by some of our cells (called melanocytes) and this melanin protects our cells from getting even more damaged by the sun. This is how we get a tan. Some people have more melanin than others, which is why some of us tend to tan easily whereas others just get burned.

Melanin is not in infinite supply, however, so when our bodies get overwhelmed by a lot of sun, DNA inside the cell gets damaged beyond repair. Damaged DNA can lead to cancer, in this case skin cancer called melanoma, but cells are clever and they detect this DNA damage, so what they decide to do is kill themselves through a process called apoptosis, or programmed cell death, to prevent themselves becoming cancerous and causing harm to the rest of the body.

Your body detects this as well, and sends a lot of blood to the area that carries cells that start the healing process, which is why your skin looks redder. This often leads to swelling as well.
Within a few days, the dead skin cells start peeling off, giving way to new skin cells.

Sun cream acts as a physical barrier that does not let the harmful ultraviolet rays get to your skin in the first place, protecting your skin cells from DNA damage. However, even they are not all-powerful so you shouldn’t stay out in the sun for too long to prevent yourself getting burned! Then again there’s not a huge risk of that in the UK..