What is the SPF number that one sees on a sunscreen bottle
How does one decide what sunscreen to buy? I thought the higher the number on the SPF, the better the protection!! Invariably I would look to buy a sunscreen that has the highest SPF number. But why would anyone buy a bottle that has a lower SPF?
Does SPF 15 mean there are 15 layers of shields around you. It’s as if there is an invisible shield around you protecting you from the harmful effects of the sun’s rays. Is it like the way the show in comic books? The way superheroes throw an invisible shield around themselves to protect them from evil weapons.
I decided to then get to the bottom of the matter. We all know that SPF means Sun Protection Factor. But what do the numbers really mean. Franz Greiter is credited with introducing the concept of Sun Protection Factor (SPF) in 1962, which has become a worldwide standard for measuring the effectiveness of sunscreen when applied at an even rate of 2 milligrams per square centimeter (mg/cm²). Hmm….. I never really measured the quantity of sun screen that ive applied per square cm of my face!
What SPF really means is the amount of time a person can be exposed to sunlight before getting sun burnt. If a person’s skin burns after 10 minutes in the sun, with a sunscreen of SPF 15, he would burn after 150 minutes in the sun. ie. 10 x 15 = 150 minutes.
SPF isn’t really the number of shields that it throws around you, but it indicates how long the cream can protect you against the sun’s rays. A standard rule of thumb that can be used is to multiply the SPF number by 10 and use that as a reference point. This also depends on the type of climate you live in. Very humid conditions where you sweat a lot may wear off the sunscreen quickly and you may have to constantly re apply. Newer sunscreens have been developed with the ability to withstand contact with water and sweat.
So, the next time you buy a sunscreen, do take into consideration the climate (dry/humid), how long you’ll be out in the sun, the number of times you need to reapply and make sure you know your multiplication.
