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 • Opinion  • Columnists  • Skincare Agony Aunt  • What’s the Difference Between SPF 30 and 50? We Ask Our Skincare Agony Aunt
Young woman applying sun cream or sunscreen on her tanned shoulder to protect her skin from the sun. Shot on a sunny day with blurry sand in the background body

What’s the Difference Between SPF 30 and 50? We Ask Our Skincare Agony Aunt

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Dr Sonia Khorana is a GP with a special interest in dermatology and Live That Glow’s own skincare agony aunt. She is passionate about helping people feel confident in their own skin.  Here, she advises a reader concerned about the differences between SPF 30 and SPF 50 , and which one is best for your skin.

Sunscreens in the UK have an SPF rating. SPF stands for ‘sun protection factor’.

It’s important to note that SPF is more accurately the sunburn protection factor and only protects against UVB rays which are responsible for skin “reddening”, or surface burns.

SPF doesn’t account for UVA rays; those are the rays that cause long-term damage including ageing and wrinkles. That’s why you need to look for the UVA star system rating on top of an SPF rating in your sunscreen (UVA rating is usually the PA +++ rating or PA*** rating on the sunscreen bottle)

In the UK you may notice a UVA star rating on the packaging along with the SPF rating. The stars can range from 0 – 5 and indicate the percentage of UVA radiation absorbed by the sunscreen in comparison to UVB radiation. That’s why it’s important to choose a high SPF as well as a high UVA protection (e.g. a high number of stars or +) and such sunscreens will be labelled “broad spectrum”.

Look for sunscreens that are broad-spectrum, water-resistant (if sweating/swimming) and have an SPF30 or higher. Broad spectrum means that the sunscreen will protect against both types of harmful ultraviolet rays (UVA and UVB).

A product with SPF 50 will protect your skin from almost 98% of the sun’s UVB rays, whereas SPF30 will protect against roughly 97%. It’s important to note that the SPF rating system is a guide to how long you can stay in direct sunlight before your skin starts to burn (remember, UVB rays cause sunburn).

Protection levels above SPF 50 only provide marginally additional coverage and no level of SPF protection can provide 100% protection, and this is why additional methods such as sun hats, seeking shade etc are advised. So, if you used an SPF 50 sunscreen and it typically takes 10 minutes until your skin starts to burn, by using the SPF 50, you’re theoretically protected from the sun burning your skin for 500 minutes (50x10mins).

But a higher SPF rating of 50 doesn’t mean you can get away without reapplying as a sunscreen’s SPF is only fully effective for two hours usually after you put it on.


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Dr Sonia is an Aesthetic Doctor and Laser Specialist who is also a GP with a special interest in dermatology, offering laser and dermatology consultations at UK-based clinics, MediZen and Kat & Co. She discusses the holistic needs of patients linked to their appearance on her Instagram @dermgp and is Live That Glow's resident skincare agony aunt, answering readers' questions on all things skin related.

Education: University of Liverpool Medical School and Queen Mary University, London

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