With summer in full swing in Australia, it’s natural to be spending more time outdoors. Picnics, beach days, backyard barbeques - It's easy to get wrapped up in the carefree summer spirit without thinking too much about our skin. We may consider the temporary flush of sunburn to be a mere annoyance, but chronic exposure to sunlight without adequate skin protection can cause long-term changes to our health.
We decided to take a deeper look at the latest science to investigate the far-reaching effects of chronic over-exposure to sunlight.
One of the most visible signs of chronic sun exposure is accelerated ageing of the skin, known as photoageing. Photoageing is caused by exposure to ultraviolet (UV) radiation and is characterised by premature wrinkles and fine lines, loss of firmness of the skin, uneven pigmentation, thinning of the epidermis, increased dryness and formation of spider veins.
At the cellular level, UV radiation inflicts damage on our skin’s DNA, which over the long term can increase our risk of developing skin cancer. UV light can damage our DNA directly, or by triggering the formation of free radicals which then damage DNA. Damaged DNA can be repaired to some extent, but repair processes may be overwhelmed with time, and recent findings suggest that the inflammatory response that accompanies UV damage can hinder DNA repair.
UV radiation also has effects in the dermis - it increases levels of enzymes in the dermis known as matrix metalloproteinases, which degrade collagen, elastin and glycoproteins, resulting in long-term damage to our skin’s structure.
A less well know fact is that UV light reduces barrier function of the stratum corneum, the outermost layer of the skin. This is thought to be caused both by changes to cell cohesion as well as damage to the skin's lipid barrier. The result is a tendency for dry, flakey skin.
However, the changes caused by UV light are not limited to physical effects in the skin. Recent work shows that UV light impacts our immune system in ways that can have profound effects on our overall health.
UV-induced inflammation accelerates ageing of the skin
It is now understood that UV-induced damage to our skin structures triggers chronic inflammation in our skin, a change that is also seen in aged skin.
This slow, grumbling type of inflammation is seen in our bodies as we age is characterised by an increase in inflammatory markers in the blood and increased numbers of senescent, or senile cells in our tissues. This chronic inflammatory process is described by some scientists as ‘inflammaging’. The inflammaging of old age is now considered to be the driving force in the development of a range of age-related diseases like cardiovascular disease, type II diabetes and Alzheimer’s disease.
The inflammaging seen in the skin following over-exposure to UV light not only increases numbers of senile cells in our skin, it also suppresses the effectiveness of our immune response. This effect is seen locally, ie in the skin, as well as in the rest of the body, to the extent that UV-induced immunosuppression can reduce the effectiveness of vaccines, and our resistance to infectious disease.
It is now considered possible that the inflammaging in our skin induced by overexposure to UV light could be one of the drivers of the inflammaging state, and therefore ageing, in the rest of our body - not just in our skin.
What does it all mean?
Although the science is still emerging, we can be confident that limiting our exposure to UV radiation is important for our overall health, not just the health of our skin. It could be a key factor not just in the ageing of our skin, but in the ageing and overall health of our bodies.
As we all know, we should protect ourselves from the sun by regularly using and reapplying broad-spectrum sunscreen, wearing protective clothing and seeking shade to reduce our UV exposure. The amount of UV radiation reaching us varies depending on our geographic location, time of day and time of year, so referring to an app that predicts UV index can help us avoid exposure to high doses. We should remember that although lighter skin burns more easily, darker skin types can still experience DNA damage and photoageing from UV light.
It is known that boosting the levels of antioxidants in our skin, both by increasing our dietary intake and applying antioxidant-rich products to our skin can reduce the damaging effects of free radicals caused by UV radiation. And as always, applying skin care that protects and restores the skin's barrier will help minimise the inflammatory effects of UV light and other skin stressors.