5 Things to Know About SPF in 2020

Sun rising above the clouds

Sun, sea and sand! The perfect formula for a holiday, isn’t it? The warmth of the sun on your face makes you smile. Being in the sun is like a huge warm hug for your body. It’s irresistible to be in the sun!

Protecting ourselves from the sun is important. Using SPF sun protection should be a top priority wherever you travel. But what does SPF actually mean? Hopefully this article will help clear up a few misnomers about SPF.

Here are the topics covered in this article:

1. SPF? What does it mean?

2. SPF 15, 30, 50? What do the numbers mean?

3. When should I use SPF?

4. How much SPF should I apply?

5. Does SPF block vitamin D production?

Daryl silhouette

SPF? What does it mean?

SPF stands for Sun Protection Factor. It is a number that represents the level of protection from the sun’s UVB rays only.

UVB rays cause the skin to burn. An easy way to try and remember this is to think that the “B” in UVB stands for BURN. UV stands for Ultraviolet rays – a type of radiation the sun emits. UV rays are invisible. Potential DNA damage from UVB rays leads to skin cancer. Wearing SPF helps to reduce the likelihood of burning. When we talk about the skin burning we mean the death of cells. Burns to the skin also cause painful blistering. Your skin cells work hard to form a protective barrier to defend your body. Look after your skin cells by wearing SPF!

Daryl and I on top of a mountain in Bali

Spf 15, 13, 50? What do the numbers mean?

My bare skin in direct sunlight will burn after 10 minutes, or so the theory goes. If I put on a generous, thick layer of SPF 15 it means I can spend 15 times longer in the sun without worrying about burning. So 10 minutes x 15 SPF = 150 minutes (an hour and a half). But wait, shouldn’t I re-apply every 2 hours? Doesn’t that mean I will burn for 30 minutes before I re-apply? Isn’t that super confusing? At the end of the day the numbers are just a technical guide. Theoretically SPF 15, if enough is applied, offers 93% protection – but that’s a 7% chance of being damaged by UVB rays! Whatever your skin “type”, wear the highest possible SPF factor you can afford. SPF 30 as a minimum. Re-apply every hour but don’t leave it longer than 2 hours!

Ask yourself these questions: Have you ever timed how long it takes for your skin to burn? I definitely would not recommend that as an experiment! The answer is that we don’t know and it’s unlikely we will find out until it happens. By then it’s too late. Prevention is always better than cure!

Think of it this way: your skin is irreplaceable and you want to prevent any type of damage at all costs. Damage can be irreversible. Frequently damaging your skin with UVB rays means that future damage is more likely.

You start to get a false sense of security once you apply a high SPF to your skin. Don’t take any chances. A higher SPF does NOT mean you apply it less often.

Daryl and I jumping in Dubai sun.

When should I use SPF?

All the time during daylight hours. The heat and intensity of the sun varies during the day but you will always be exposed to UV rays. The closer you are to the sun, the higher your exposure to UVB rays. That means it’s even more critical to wear SPF when you are on a plane or climbing a mountain!

As the Earth rotates towards the sun your exposure is higher too. That’s why between 10am and 4pm there is the highest risk of getting burned. Makes sense now, right? So stay out of the sun, seek shade or cover up during those hours of the day. Easy!

Always apply at least 30 minutes before being exposed to the sun. Re-apply every hour while you are in the sun until sunset.

Daryl and I smiling in the sun in Indonesia

How much should I apply?

Do you know your skin surface area in meters? I certainly don’t! It’s especially confusing when the recommended amount of SPF to apply is given in spoonfuls, shotglass or millilitre measurements. You aren’t going to be measuring creams or sprays with tablespoons- especially not at the beach or on top of a mountain! If you don’t apply enough then you are not protected. So re-application is super important because most people don’t put enough on in the first place. Re-apply after sweating, being in water for over 30 minutes or rubbing your skin with anything.

Think of it this way: when you moisturise your skin you feel good in some areas and still a bit dry in other parts, right? The fact is you can’t apply too much moisturiser – it’s always good for your skin to be hydrated. The same goes for SPF application. Put enough on dry skin so you can feel a relatively thick layer on your skin. Always put SPF on before anything else! If you know you will be exposing certain body parts put more than you think you need. You can’t go wrong. The most exposed area will always be your face – don’t forget your ears and the back of your neck!

When I apply SPF I put a big blob on my hand and see how far it goes. If you can’t see a difference in skin texture you haven’t got enough on. You want to be shiny to reflect those UVB rays 🙂

sun reflecting on water
Sun near Komodo Dragon Island, Indonesia

Does SPF block Vitamin D production?

Your skin does use sunlight to help make Vitamin D. But, as we have seen, the risk of damaging your skin in the sun is not worth it. There are safer ways to get Vitamin D. Use Vitamin D supplements or eat foods which are high in Vitamin D.

silhouette photography of group of people jumping during golden time
Photo by Belle Co on Pexels.com


SPF is a way to measure protection from the sun’s UVB rays. Always put on more than you think you need and re-apply as often as every hour. Get your Vitamin D from supplements and food instead of the sun to limit skin damage.

I really hope you enjoyed this article and learned something new!

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I am a UK GPhC registered Pharmacist in London

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