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SPF Sunscreen Ratings Explained

A survey by the American Academy of Dermatology has shown that the majority of respondents didn’t actually understand the SPF ratings.

Only 32% understood that SPF 30 does NOT provide double the protection of SPF15.

It’s important that everyone understands what they are seeing on a sunscreen label.

A sunscreen with an SPF of 30 blocks up to 97%of the sun’s rays.

Higher SPFs block slightly more rays, but a higher-number SPF does not allow you to spend more time outdoors without reapplication; all sunscreens should be reapplied every two hours, or after swimming or sweating.Dr. Abel Torres, president of the American Academy of Dermatology (AAD).

SPF Ratings Explained:

SPF ratings are calculated in a laboratory setting and as such should be treated as estimates. The figures work as follows:

  • SPF 50 allows an estimated 1/50 of the sun’s burning rays through to the skin (which equates to 98% protection)
  • SPF 30 allows 1/30 of the sun’s burning rays through to the skin (which equates to 97% protection)
  • SPF 15 allows an estimated 1/15 of the sun’s burning rays through (approximately 93% protection)

In terms of how long you can stay in the sun, the theory is that if it takes 20 minutes for unprotected skin to start turning red, using an SPF 15 sunscreen prevents reddening 15 times longer — about five hours.

However, it is important to note that actual protection will vary. Results also depend on whether the right amount has been applied and reapplied regularly as well as after swimming or sweating.

In addition, good sunsense advice also includes staying out of the sun at peak times and covering up with hats and longer clothing.


Dr John Tanqueray of Mulberry House Clinic & Laser Centre has produced a video to explain the importance of sunscreen. He says:

When we’re thinking about skincare and skin protection, one thing we should never ignore is use of a sunscreen.

We now know that sun is damaging to the skin, both in terms of causing ageing problems, pigmentation problems and even, later in life, causing skin cancers.Dr John Tanqueray

Sunscreen – Sun Protection and Skincare

ZO Skin Health Sunscreens

Dr John Tanqueray introduces 3 main sunscreens in his video:

  1. SPF 30 primer – smooth and soft on the skin and ideal under makeup, making it a popular choice
  2. SPF 50 – waterproof and water resistant. Tint increases with massage so the finish can be adjusted to suit skin tone
  3. SPF 50 body spray – ideal for holidays


ZO Skin Health

The ZO Skin Health regime includes an extensive range of skincare products. More information about ZO Skin Health and prescription skincare.

Mulberry House Clinic & Laser Centre

Established 2003

Mulberry House Clinic & Laser centre stands out in the Northampton area as an independent practice with over 10 years experience. Cosmetic skin treatments are carried out by Dr John Tanqueray, who also works with Allergan to train other professionals in his skills and techniques.

For further information or to arrange a confidential consultation, please complete our contact form, call 01604 702630 or email: info@mulberryhouseclinic.co.uk.

Article Name
SPF Sunscreen Ratings Explained
Dr John Tanqueray explains why sunscreen is essential to skincare and introduces ZO Skin Health range of sunscreens, available at the Northamptonshire clinic.