JOURNAL 21: A guide to SPF
Ultraviolet light
Exposure to ultraviolet (UV) light produced by the sun, repeated over time, eventually begins to damage the DNA of our skin cells, resulting in a loss of DNA integrity and subsequent mutations to our DNA. This means that eventually our body is unable to produce ‘normal’, healthy, proper-functioning skin cells and instead begins to produce unhealthy, dysfunctioning skin cells. Furthermore, this DNA damage can be cancerous, which leads to mutations in DNA that produce cancerous skin cells, such as squamous cell carcinoma (SCC) and melanoma – types of skin cancers.
Over time, repeated UV exposure also depletes our skin of its natural antioxidant defences, causing oxidative stress, which further damages the DNA of our skin cells and contributes to the increased production of unhealthy, dysfunctioning skin cells.
The production of poor quality, unhealthy, dysfunctional skin cells causes them to appear damaged or ‘aged’ to the naked eye. Since our skin is composed of trillions of skin cells, then trillions of poor-quality, unhealthy, dysfunctional skin cells equals visibly damaged or aged skin.
UV exposure further damages our skin by disrupting the natural production of collagen and elastin – the proteins responsible for giving our skin its suppleness, strength and elasticity. It triggers an enzymatic reaction that breaks down collagen and elastin within the body, so while our bodies are always working hard to produce collagen and elastin (which naturally declines as we age), UV exposure is working to break it down or hinder the process.
If you have ever had an intensive skin treatment designed to ‘promote collagen production’, your skin therapist has probably told you to avoid UV exposure for some time afterwards. This is because UV exposure is going to undo the collagen production, just as quickly as your body is working to produce more.
It is important to note that sun damaged or aged skin does not suddenly appear overnight, but rather it is a culmination of repeated, daily UV exposure over years and decades, with a few episodes of sunburn thrown in here and there for good measure. For this reason, it is never too early to start looking after your skin.
Sun protection factor
It is commonly believed that the higher the sun protection factor (SPF), the higher the level of UV protection, however there is actually only a very small (5%) difference in the level of UV protection offered between an SPF 15 and an SPF 50 (93% protection versus 98% protection).
What SPF actually relates to is the unique UV exposed burn time of your skin.
For example, if your natural UV exposed burn time (the amount of time where your skin cells start to react, not necessarily burn) is 10 minutes, then using an SPF 15 sunscreen means that, ideally, you are extending your skin’s natural UV exposed burn time by 15 times longer than this, so up to 150 minutes (10 X 15 = 150). Based on this, wearing an SPF 50 rated sunscreen would extend your burn time by 50 times, so up to 500 minutes (10 X 50 = 500).
It is important to note that this is not an exact guide (no one should be exposed to the sun for 500 minutes and rely on one single application of sunscreen). Everyone’s skin is different and there are many factors involved (genetics, water, UV index, time of day, weather, location, altitude, seasons etc.) that alter your skin’s natural UV-exposed burn time, which therefore alters how often you need to reapply sunscreen. SPF should be used to give you a better idea of how often you need to reapply your sunscreen.
Another important thing to note is that SPF + SPF does not equal a higher SPF. For example, if you apply sunscreen with an SPF 15 and then apply make-up with an SPF 20, this does not equal an SPF 35. You are only ever protected by the highest SPF, in this case SPF 20.
Kismet Health Skin Healing Cream
Physical v chemical sunscreen
For a few years now there has been much debate about chemical versus physical sunscreens and which is better.
It is typically thought that chemical-based sunscreens absorb UV rays (convert them into heat and then release them from the body) and that physical sunscreens scatter or reflect UV rays, however this is not entirely true.
According to studies, physical sunscreens scatter or reflect no more than 15% of UV rays. The remainder is absorbed, just like a chemical sunscreen, meaning both chemical and physical sunscreens absorb UV rays.
Both chemical and physical sunscreens are equally as effective as one another, and one isn’t better than the other, they just work in slightly different ways.
So how do you choose a sunscreen?
My advice is to choose a sunscreen based on the non-active ingredients and what impact they will have on your skin cells. Select a sunscreen that is free from fragrances, colours, dyes, preservatives, emulsifiers, sulphates etc. as these can irritate the skin.
Physical sunscreens are ideal for sensitive skins as they typically contain fewer chemicals, meaning they are less likely to cause skin irritation. They do, however, tend to contain zinc oxide, which can make them quite thick and therefore sit heavier on the skin. This can lead to surface blockages (breakouts) so people with oily, congested and acne-prone skin need to be mindful of this.
On the other hand, chemical-based sunscreens typically contain between 3–4 chemical compounds in the one sunscreen and are therefore more likely to cause skin irritation than physical sunscreens. They are, however, more light-weight and don’t sit as heavy on the skin and therefore have their place with people who suffer from oily, congested and acne-prone skin.
How do you apply sunscreen?
Sunscreen needs to be applied at least 20 minutes BEFORE exposure to the sun. This gives the active ingredients time to settle into the skin and take effect – the effectiveness of sunscreen is all in the time it is given to absorb into the skin and start working.
Applying sunscreen just before you jump in the water or while you are sitting out in the sun does not actually give you proper protection. You need to apply it as you are getting ready to leave the house.
You also need to re-apply your sunscreen following each time you jump in the water, as sunscreens are not waterproof and they do wash off.
Apply sunscreen to all the areas that won’t be covered by clothing and remember the front and back of the neck, your ears and the tops of your feet!
If you would like to work with one of our naturopaths, please feel free to book an appointment to discuss your individual circumstances.
Written by Perri Baldwin BHSc
Naturopath
