We invited founder of Decree, Dr AJ Sturnham, who has 15 years clinical experience and worked as a GP specialising in dermatology and aesthetics, to answer our burning questions.
Q. What does SPF actually mean?Sun Protection Factor (SPF) is a measure of a sunscreen's ability to prevent UVB rays from damaging the skin. For example, if it takes 20 minutes for your unprotected skin to start turning red and burning, using an SPF 15 sunscreen theoretically prevents your skin from burning 15 times longer, about five hours.
As most SPF products' protective powers degrade within 2-3 hours, I recommend reapplying your product at these time intervals.
What an SPF rating does not take into account are the other harmful UVA rays our skin is exposed to, which penetrate deeper into the skin and can cause damage at the DNA level. SPF ratings measure the amount of UVB ray protection only. You then need to factor in the UV ray intensity. UV rays are strongest in areas close to the equator and also intensified at high altitude, in areas of snow and when on the beach. Reflective surfaces such as snow or ice, bounce back up to 80 percent of the rays so that they hit the skin twice.
Q. If the SPF factor is the same, does this mean this protection is the same?
The SPF factor refers to a product's ability to protect your skin from UVB rays. You also need to assess a product’s UVA rating too. UVA rays are the ageing rays that are present all year round.
I recommend that all of my patients use a daily skincare product that contains both UVA and UVB protection, a minimum factor 30, ideally 50 and a 5 star UVA rating.
There are two basic types of ultraviolet rays that reach the earth’s surface, UVB and UVA. I keep it simple by saying ‘B’ rays are the ‘burn’ rays and ‘A’ rays are the ‘ageing’ rays.
UVA rays account for up to 95% of the UV radiation reaching the Earth's surface. Although they are less intense than UVB, UVA rays are 30- 50 times more prevalent. Unlike UVB rays, they are present all year round with relatively equal intensity during all daylight hours and can even penetrate clouds and glass.
So whilst most of us focus heavily on getting the UVB protection right, by looking at the SPF rating, we often neglect the UVA part and forget to check a product’s UVA rating and ingredients. UVA rays penetrate the skin more deeply than UVB rays and are thought to play a major part in skin ageing(photoaging), UVA rays also play a role in skin cancer formation.
UVB rays have a shorter wavelength and attack the surface layers of the skin. They cause reddening and sunburn as they damage the skin's more superficial epidermal layers. Its intensity varies by season, location, and time of day. UVB rays do not significantly penetrate glass.
q. what advice do you have to applying spf?
Before applying your SPF layer, I recommend using an antioxidant serum such as the Decree Protect Elixir. Top pick ingredients to look for are Vitamins C.B, E and Ferulic acid. These antioxidants work in synergy with your UVA and UVB blockers, to protect the skin from environmental stressors. Most sunscreen protective ingredients become less effective as they start to break down 2-3 hours after application.
If you burn with a product, then the chances are you are not applying enough product and / or that you are not applying regularly enough. Most SPF products degrade within 2-3 hours. For this reason, we recommend reapplying your product every few hours for maximum protection.
When tests are done to establish a product’s UVA star and UVB SPF rating, it is first tested in a lab, with ‘in vitro’ analysis and then tested on humans, with ‘in vivo’ analysis. An SPF rating is awarded based on assessments which show that a product can protect the skin for a proven period of time.
These assessments are based on using 2mg per centimetre squared of product, which equates to approximately a quarter of a teaspoon of product for the face and neck or a 10 pence pieced sized product for the face and neck. If you apply a pea sized amount of an SPF 30, for example, you are likely to only achieve an SPF protection of 5-10. P20 has been clinically proven to provide 10 hours of protection.
meet dr aj's skincare brand, decree
Calibrated to meet your natural tolerance, Decree skincare gives you maximum results. With a simple, concise product line up, separated into a Daily and Weekly regimen, you will receive therapeutic doses of formulated skincare consistently, which is key to healthier, more youthful, beautiful skin.Discover Decree