What is sunscreen SPF?
By Kidspot Team

Most people know that the higher the SPF rating on a tube of sunscreen or moisturizer, the more protection it offers from skin cancer and melanoma.

SPF stands for “sun protection factor” and is a scientific measurement used to indicate the amount of ultraviolet radiation (UV rays) protection the product can provide. 

Most sunscreen and skincare products in New Zealand are labeled SPF15, SPF30+, or SPF50+. These numbers can cause confusion as some people may mistakenly think one is giving twice as much sun protection as the other. Here’s what you need to know on “What is sunscreen”.

The low-down on sunscreen SPF

A broad spectrum sunscreen of SPF 15 blocks approximately 93% of UV rays whilst one of SPF 30 blocks approximately 96% of UV rays.

According to the federally-run Australian Radiation Protection and Nuclear Safety Agency (ARPANSA), a sunscreen with a rating of SPF15+ would provide a fair-skinned person 15 times more protection for their exposed skin than if they didn’t use a sunscreen.

What this means is that if a fair-skinned person starts to redden after 10 minutes in the sun, then correctly applying SPF 15 sunscreen will provide protection for 15 times longer, in other words, 150 minutes of protection before they redden. 

“It is important to remember that after 150 minutes in the sun while wearing sunscreen this person would still have received the same UV rays exposure as they would have received in 10 minutes if they had not been wearing sunscreen,” says an ARPANSA spokesperson. “In both cases their skin has received the same amount of ultraviolet radiation exposure.

“In practice the amount of sunscreen applied and the evenness of the coverage can have a significant affect on the duration of protection offered by the sunscreen.”

Remember, sunscreens of less than SPF15 offer only moderate to low protection. Sunscreens that claim 30+ or more provide a higher level of protection.


Understanding sunscreens


There are two main types of sunscreens. These are:

  • Chemical filters: This is the most commonly used sunscreen in New Zealand and works by absorbing the UV rays as it reaches the skins, counteracting the rays to reduce skin damage. These sunscreens are often easy to apply so will be used on larger areas of the body.
  • Physical blockers: This type scatters or reflects UV rays from the skin. Two common active ingredients for blockers include zinc oxide and titanium dioxide. 

ARPANSA has these words of warning: “Remember that the purpose of using sunscreens is to reduce UVR exposure, not to extend the time spent outside in the sun.”

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This article was written for Kidspot, New Zealand's best family health resource, in conjunction with NIVEA SUN. Sources include Australian Radiation Protection and Nuclear Safety Agency, and Kidspot Australia.
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