It’s well known that sunscreens are recommended to protect you from skin cancer. But do you know how they work?
Here’s a quick overview to help you stay safe in the sun and at the same time protect our oceans by making sure your sunscreen is reef safe.
What is Sunlight?
Sunlight is electromagnetic radiation from the sun which is basically packets of energy called photons that travel in wavelengths. Our skin contains molecules that absorb this energy and, via a chemical reaction, converts it into something the body can use, for example Vitamin D.
However, some of the chemical reactions can cause damage to the skin which can lead to collagen degradation (wrinkles) and skin cancers.
For our sunscreen overview we are concerned with UVA and UVB light:
- UVA causes photo ageing such as wrinkles, loss of collagen and formation of brown spots.
- UVB causes burning of the skin.
There are two types of sunscreens: Chemical and Physical.
Chemical sunscreens are absorbed into the skin. As they sit in the upper layer of the skin they absorb UVA and UVB rays, and convert them into heat, which is then released out of the skin, thus stopping the UV rays from doing harm.
- Less is needed to protect the skin
- Spreads more easily on the skin as it tends to be thinner
- Works after about 20 minutes after application. Which means you need to wait before going out into the sun after applying it
- Increased chance of skin irritation due to the multiple ingredients combined in order to achieve UVA and UVB protection
- The higher the SPF, the higher the chance of skin irritation
- Re-application is more frequent as the protection it offers is used up quicker in direct UV light
- Increased chances of rosacea-prone skin types because it changes UV rays into heat which can exacerbate flushes
- Possibly increase existing brown spots and discolouration due to a higher internal skin temp
- May clog pores in people with oily skin types
Physical sunscreens sit on top of the skin to deflect and scatter UV rays.
- Naturally broad spectrum meaning it offers protection against both UVA and UVB rays
- Protection as soon as applied, so there’s no need to wait before going out in the sun
- Lasts longer than chemical sunscreen, when in direct UV light but not when doing physical exercising/sweating/getting skin wet
- Better for sensitive skin as it’s less likely to cause skin irritation
- Better for those with heat activated skin conditions such as rosacea and redness because it deflects heat and energy given off by the sun, away from the skin
- Ideal for acne-prone skin as it’s less likely to cause pore-clogging
- Longer shelf life
- Easily comes off by rubbing, sweating, going in water, which means more frequent application under circumstances that cause this e.g., exercise or swimming
- Needs to be applied thoroughly and generously otherwise it can be less effective than chemical sunscreen
Sun Protection Factor, or SPF, tells you how long you can stay in the sun, whilst wearing sunscreen, without getting burnt.
So SPF 15 means you can stay in the sun 15 times longer with sunscreen on than without.
SPF 30 means you can stay in the sun 30 times longer with sunscreen on than without.
For example, if you burn in the sun in 10 minutes without sunscreen, with sunscreen SPF 15 it will take 15 times longer to burn. So it will take you 2.5 hours to burn in the sun.
A higher SPF doesn’t mean the sunscreen is superior, it means you will be protected in the sun for a longer period of time.
SPF only indicates protection levels against UVB rays. So for the best protection look for UVA and UVB protection.
SPF is measured based on the application of 2 milligrams (mg) of sunscreen for each square centimetre (cm) of skin surface. Roughly 6 full teaspoons to cover the average adult body. Most people don’t apply enough sunscreen. They usually apply a quarter to a half of the amount required.
Using half the amount required only provides the square root of the SPF. This means that half the application of SPF 30 sunscreen only provides an effective SPF of 5.5. So if you burn in the sun in 10 minutes without SPF on, then applying half the required amount of SPF 30 means you can stay in the sun for 55 minutes before having to apply sunscreen again.
To be safe, it’s advised that you reapply sunscreen every 2 hours.
Did you know some sunscreens can harm our oceans?
Coral reefs around the world are slowly eroding due to climate change, pollution and other environmental factors.
One of these factors is sunscreen washing off when you go for a swim or have a shower.
Extensive research, on more than 50 sunscreen brands, found that Oxybenzone and Octinoxate are the main culprits of coral bleaching. Hawaii and Florida have banned these ingredients in Sunscreen.
They’ve made a list of substances that pollute and damage marine life called the ‘HEL List’, which is copied below:
- Any form of micro plastic spheres or beads.
- Any nanoparticles like zinc oxide or titanium dioxide.
- 4-methylbenzylidene camphor
- Para-aminobenzoic acid (PABA)
There are now some products labelled ‘Protect Land + Sea’. This is a certification seal that means the product has been tested in a laboratory, using specialised techniques, to verify that the product is completely free of chemcials on the HEL list.