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How Much SPF Do You Need? Top Dermatologist Tells All!


Dermatologist and NHS clinician Dr Thurein Ne Win shares his expert advice for staying sun safe all year round.

July 01, 2021


Photo showing a close up shot of a hand as another hand squeezes SPF from an orange bottle into the palm

July 01, 2021


This summer may not have brought the sunny weather we hoped for, but it’s still important to remember to protect your skin from sun damage.

We all know we should wear SPF, but how much, how often, and does it really matter if we don’t apply it all year round? Let’s take a look at these questions and more!

First off, why do I need SPF?

We need to wear SPF to protect our skin from UV rays, or ultraviolet rays. They come from the sun and can damage the skin. There are two main forms of UV.

Graphic listing the differences between UVA and UVB rays and how they affect the skin

UVB rays have a shorter wavelength, and penetrate the top layers of the skin. They cause skin burning and are proven to cause melanoma and non-melanoma skin cancers, including basal cell cancer (BCC) and squamous cell cancer (SCC). It’s important to familiarise yourself with the signs and symptoms of skin cancer and if in doubt, get it checked out. Visit your GP who will then refer you to a dermatologist via the most urgent system, known as the 2 week wait system, if they are concerned.

UVA rays have a longer wavelength and penetrate through to the dermis, or deeper layer of the skin. They cause damage to the vital structures of the skin, including collagen and elastin, which results in photo ageing, aka premature signs of ageing in the skin. They also cause damage to the eyes and structures around the eyes - so please remember to keep those shades on! Additionally, UVA can also cause accumulated damage to the DNA of skin cells and also result in cancer, meaning they are equally as important to protect yourself against.

Remember - it’s especially important to protect children from the sun. A sunburn under the age of 15 predisposes you to a higher risk of skin cancer later in life, so take extra care to keep your little ones topped up with SPF.

What factor SPF should I use?

So, we know we need to protect ourselves against UVA and UVB - but what’s the best SPF to use? I recommend using Factor 30 as a minimum, but ideally a Factor 50 SPF product for the greatest protection. Remember, SPF is not the be all and end all of your sun care routine; you should use Factor 50 alongside other protection such as staying in the shade, wearing a wide-brimmed hat and sunglasses, avoiding sun during the hottest point of the day, and wearing clothing that covers and protects you.

Do I need to wear SPF all year round?

Yes, I would recommend Factor 30 all year round. This is because UVA rays enter the Earth’s atmosphere at the same levels all year round, and these rays are not filtered by either clouds or windows, so even on an overcast day - even a rainy day! - it is still beneficial to wear Factor 30 SPF to protect yourself from those invisible UVA rays. Don’t be fooled by thinking only sunny days can cause sun damage. I have seen people develop skin cancer on their forearms just from driving without SPF protection, so it really does make a difference.

Does my skin tone affect how much SPF I need?

People are often misinformed about whether those with darker skin need to use SPF as much as those with lighter skin - basically, as long as you have skin, you should be using Factor 30 minimum. Unfortunately, I often see people with darker skin experiencing worse results when they get skin cancer, so although melanin may prevent skin ageing and provide a small amount of natural protection, the risk of sun damage and skin cancer is still very real, and often goes undetected until later stages. This is sometimes due to the false belief that dark skinned people cannot get skin cancer, and sometimes due to the skin cancer presenting in an unusual place, such as beneath the nails. 

If you do have dark skin, you may want to choose an SPF product that doesn’t leave white marks on the skin; happily, there are several “invisible” types of SPF product on the market to choose from. 

And for lighter skinned readers, remember, getting a tan may make you feel good but it isn’t a good sign. It actually means your skin is not tolerating the UV rays, and is trying to darken to protect you. My advice is if you feel you must have a tan, get a fake one, as there are plenty of great products for this.

How much SPF do I need?

Many people don’t actually know how much SPF they need. There are various methods of calculating how much to use; for instance, the finger length method, which is where you squeeze suncream along the length of your index and middle fingers, although this only works if you use traditional suncream rather than a spray. If you are using a spray, make sure to get an even sheen across all areas of the face and body for consistent protection. If in doubt, always use more and err on the side of caution!

Graphic showing how to spply the right amount of SPF by measuring it out using the middle and index finger of the hand

In terms of how often you should apply SPF, I recommend applying it every 2 hours, and hourly if you are sweating a lot or swimming - basically, if there is anything causing the SPF to wash away. Remember to cover all exposed areas including overlooked places like ears and feet, and even lips - you might want to use an SPF lip balm for this. Also, apply a gentle dab onto your eyelids - but be careful not to get any in your eyes themselves!

How do I choose the right SPF product?

There are a couple of different types of sunscreen. The physical sunscreens, also called blocker types, have titanium dioxide and zinc oxide, which are natural minerals that sit on the skin and reflect the UV rays away. For this reason, they may also be called mineral sunscreens. 

The other type is chemical sunscreens, which contain chemicals that actually absorb the UV and dissipate it. Chemical sunscreens are often easier to rub into the skin without leaving a white residue, but they are also less natural and some people have concerns about the chemicals being absorbed. That being said, there is no evidence that any approved chemical sunscreens will cause any harm. You should apply chemical SPF around 30 minutes before going outside for it to work properly.

When it comes to SPF brands, expensive doesn’t always mean better. Try a few and see which one you get on with the best - using either type of sunscreen is better than using none at all, after all! 

Make sure any sunscreen you choose is broad spectrum, and protects from UVA and UVB rays. Choose products that have a 5 star rating for protection against both UVA and UVB - for instance, Aldi’s Lacura range has a maximum 5 star UVA rating compared to more expensive brands which only have 3, which actually makes it one of the best on the market currently!

Additionally, the brand Altruist has been formulated by a UK dermatologist and is available on Amazon, and is essentially minimal or non-profit.

And finally - if you’re wearing makeup, SPF should be the final step of your routine. It is far better to use a specific SPF product rather than relying on SPF within your makeup, even though there are several creams and foundations which now contain some SPF protection. If you rely on SPF in your makeup, chances are you simply aren’t going to have adequate protection, as you would need to really layer the makeup on extremely thickly.

Stay safe out there and enjoy the sun responsibly!

 Photo showing Dr Thurein Ne Win alongside a short biography about his expertise as a dermatologist