How does the Sun really damage our skin on a cell by cell basis over time
So we have all witnessed the casual creep of an emerging sun burn. I once realized that I had
missed a hand shaped section on my back when a wicked burn emerged several hours later and I bore the mark of a tanned handprint for a month later. So we all know the general gist of how it works- we expose ourselves to sunlight and if not properly protected- we get sunburnt or perhaps a perceived lovely glow. In the back of our minds, we know that perceived glow might turn on us. We can spot sun damage with its entailed leathery texture of skin, pigmentation, freckles (yes that is sun damage, no you are not born with them) wrinkles and laxity. However, what damage is done in the moment and immediately after. How is the trauma inflicted? For those who are curious, here is a timeline for sun damage beginning with the first part in this series- the sunburn.
Moment 0: Vasodilation
Imagine a pure and perfect length of unprotected naked skin, while the first few rays of sunlight reach out and touch it. It’s a fantastic sensation for many but the pleasure hides the unseen assault that is happening.
Of the UV light that is not absorbed by the ozone layer, 5% of it is UVB- the burning rays. Think of UVB as being the heavy weight brute of the UV family. They pack a heavy punch that cause an immediate reaction. Immediately, the UV light triggers vasodilation, meaning a surge of blood rushes to the skin. This explains why you see an immediate reddening of the skin. However, this merely a first glance of what is to come as the more pronounced erythema (skin reddening) will appear 1 hour later and then peak between 24-48 hours.
If the skin is truly naked and without any form of protection, then the other 95% of UV light in the form of UVA will begin its more insidious invasion. Studies have shown that UVA also has an effect on vasodilation- however, it’s effect tends to peak after 72 hours. If you find your sunburn peaking or continuing substantially 3 days after exposure, it might be a good indicator that you were unprotected against UVA light in addition to UVB. This very often happens during those cloudy days where you receive the unexpected worst sunburn of your life.
Multiple studies have been conducted to find ways to mediate UVB and UVA caused erythema. Aspirin due to its possible inhibition of a fatty acid called prostaglandin showed the best improvement for UVB caused erythema. It did not show the same improvement for UVA caused erythema- leading researches to conclude that a different physiological effect was occurring with UVA based vasodilation.
Other research also showed that the DNA of skin cells are one of the main targets of UVB light.
In other words, DNA are like sponges that soak up UV light, which causes a multitude of issues. DNA’s exposure to UV light immediately coincides with the production of a DNA repair enzyme that leads to a reduction in erythema. This means that from Moment 0 of UV exposure- an intricate anti-inflammatory response is triggered as the body fights to repair itself.
There is an upside to sunburn, as unpleasant as it sounds- you can consider it an undeniable warning sign that you should get out of the sun. The issue with many high SPF sunscreens is that they mute that early detection system but do not necessarily follow up with the requisite UVA protection to keep other forms of skin damage at bay.
Something to think about until next time when we explore the physiological response within your skin as sun damage progresses.