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The 5 Rules Of Using SPF – The Science Of Summer Skin

How Should You Use SPF?

It’s been suggested by dermatologists and doctors that upwards of 80% of all skin ageing is due to sun damage. From pigmentation to wrinkles and even dark spots, UV rays can cause them all.

When we are exposed to sunlight, our bodies engage a natural defence in order to protect our skin. We produce melanin, which is delivered to our skin from cells called melanocytes, and its job is to absorb ultraviolet light emitted from the sun and dissipate its heat. When these defences are overwhelmed and we reach our limit of melanin production, a toxic reaction occurs, resulting in sunburn.

In the medical world, sunburn (also known as erythema) is described as the dilation of the capillaries under the skin, due to inflammation or infection after the above toxic reaction takes place. These symptoms and reactions don’t occur right away – they usually begin around 6-12 hours after the damage has been done, so even if your skin feels fine after your day at the beach, you could face waking up looking like a lobster!

By protecting our skin from these harmful forms of radiation, and therefore the impending overwhelming of your natural defences, you can keep your skin looking youthful and healthy and even prevent the onset of further ageing.

The best way to protect your skin against sun damage without staying in the shade for the entire season, is using an effective sunscreen with SPF – or ‘Sun Protection Factor’ – with adequate protection levels.

Sunscreen works in two ways to protect you from the damage mentioned above: it either absorbs the UV wavelengths, or scatters and reflects them. Depending on the makeup of your sunscreen, the SPF value will vary.

To ensure you understand how to best use your SPF, we’ve put together these 5 easy-to-follow rules:

1. When do I need to apply SPF?

Most people only use sunscreen on vacation, but it’s important to wear some form of protection every day, even if it looks cloudy and grey outside. The sun’s rays can penetrate your skin even through cloud, so it’s important to ensure you’re protected. If it’s a hot day and you’re in direct sunlight, most dermatologists advise applying every 2 hours, particularly for your face. Depending on the SPF value of your sunscreen, the rule tends to be that if you tend to burn in 10 minutes, and SPF of 15 would protect you for 150 minutes. An SPF of 30 would protect you for 300 minutes… and so on.

2. How much do I need to use?

It’s hard to measure, but there's actually a science to it! It’s suggested that you need 2mg per square cm of skin, or in other words, about ½ teaspoon to cover your face and neck. Remember though, just because you double the amount put on, it doesn’t mean you’ve doubled your protection! The higher the SPF value, the higher the percentage of protection – for example, Factor 15 filters around 92% of radiation, a Factor 30 will absorb 96%, and a Factor 40 will absorb 98%... so to ensure maximum protection, always go for a higher SPF rather than layering up your Factor 15.

3. What’s the best way to apply it?

The number one rule is ‘don’t rub too much!’ – you want most of the product to sit on your face, not on your fingertips! The trick is to apply it in stages. Massage in a little, let it dry, then apply another layer until you’re fully protected. You should try to apply around 30 minutes before your time in the sun, which will let the protective compounds in sunscreen work their magic deep into the skin. For ultimate protection, you want your sunscreen to contain both organic compounds and inorganic compounds that defend against UVA and UVB.

4. What if my makeup has SPF in it?

Unfortunately, although this will protect you on those aforementioned cloudy days, it’s not quite enough to reach that 2mg/cm rule. The best idea is to wear a non-greasy sunscreen underneath your foundation, let it dry, then apply your makeup as usual! By protecting your skin each morning before your makeup is applied, you can help to reduce the onset of wrinkles and dark spots caused from the sun’s radiation.

5. Can sunscreen expire?

Yes! It’s extremely important to check if your sunscreen is still in date before use, otherwise you might be putting in the work for no reward. Most mainstream brands last for around 2-3 years, but it’s worth buying new supplies every season. If you cover your skin in an out-of-date sunscreen, you will be putting yourself at risk of not only cosmetic damage and visible changes associated with ageing, but also your risk of skin cancer. The sun is public enemy number one when it comes to this awful skin disease, and it’s suggested that 1 in 5 American’s will develop skin cancer in their lifetime. With this figure in mind, using an effective SPF should be a daily priority.

Final Thoughts

All in all, I think the majority of us underestimate the importance of wearing sunscreen and protecting our skin against sun damage. Apart from living your life inside a shady bubble, there really isn’t much we can do to avoid sunlight. So the best plan of action we can take is to educate ourselves on the best methods of protection.

Cel Pro Tip: Make sure your sun cream has an adequate SPF level, ensure it’s in date, apply as regularly as you can, and take breaks out of direct sunlight whenever possible.



Rachel Cleverley


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