What is the difference between SPFs?
Cara Ho
What is the difference between SPF’s?
SPF stands for Sun Protection Factor, and it indicates a sunscreen’s ability to block UVB rays. The concept was pioneered at the Coppertone Solar Research Center in 1972; in 1978, the FDA published an SPF method based on Coppertone’s system, according to Dr. David Leffell, Chief of Dermatologic Surgery and Cutaneous Oncology at Yale.
The numbers themselves stand for the approximate measure of time a person who has applied the sunscreen can stay out in the sun without getting burned. Say you get burned after 20 minutes in the sun without sunscreen; if properly applied (and reapplied), SPF 30 will allow you to stay in the sun 30 times longer without burning than if you were wearing no protection at all. So, theoretically, you should have approximately 600 minutes, or 10 hours, in the sun. But it’s not an exact science because the amount of UV light that reaches us depends on a number of factors, including cloud cover, the time of day, and the reflection of UV rays off the ground, so it’s generally recommended that you reapply sunscreen every two hours (or even sooner).
It is important to note that the SPF factors are calculated by rounding down the time required to burn; however, you may get a false sense of protection from an SPF because the amount of sunscreen used in the tests is a lot more product than the average person uses. The tests use 2 milligrams of formula per square centimeter of skin.
What gives a sunscreen a higher SPF comes down to the product’s formulation. It’s possible that an SPF 50 might contain slightly more of one or more sunscreen active ingredients to achieve that higher SPF but it’s also possible that the SPF 50 might contain an additional active ingredient to help boost the SPF performance to SPF 50.
But no matter what SPF your sunscreen is, you’ll still get a burn if it’s not properly applied. So let’s go over how to do that.
HOW TO APPLY
First, make sure you have a water resistant, broad spectrum sunscreen—which means that it protects against both UVB and UVA radiation—with an SPF of at least 30.
Twenty minutes before you go out to the beach or the pool, begin to apply your sunscreen in an even coat. Don’t apply it like icing on a cake, unevenly applied sunscreen, is not a good sign. Sunscreen sprays will easily give you that even coat you need.
Whether you’re using lotion or a spray, when it comes time to apply, start with your scalp and face, even if you plan on wearing a hat. Make sure you’ve covered the ears and nose and under the eyes. Then, I would move down to the shoulders, and make sure that someone can apply the sunscreen on your back beyond the reach of your hands.
Other areas that are important that you may forget to cover, but shouldn’t, are the tops of your feet, the backs of your hands, and your chest. We see it all the time now—the v of the chest in women has become a socially and aesthetically huge issue when they are 50 and beyond. Because even though they can treat their faces with all sorts of cosmetics and procedures, the chest is much harder, and they are stuck with the face of a 40 year old and the chest of a 60 year old. You want to avoid that using sunscreen.
Another important thing to keep in mind: Water resistant doesn’t mean waterproof. I always tell clients to reapply every couple of hours while you’re active outdoors and always reapply when you come out of the water or if you’ve been sweating a lot, regardless of whether the label says water resistant.
Determining whether or not you’ve succeeded in properly applying your sunscreen is easy: You know you’re applying your sunscreen properly if, after the first time you’ve used it, you haven’t gotten a burn.
There is a caveat, though: It’s not a good idea to think of sunscreens only as a way to extend your time in the sun. One must also understand that even before becoming sunburned, your skin is receiving UV exposure that causes other damage to the skin. At the end of the 600 minutes, you will have accrued enough UV to cause a sunburn—one Minimal Erythema Dose or MED—but there is pre-MED damage done to skin cells’ DNA and to the skin’s supporting structure of collagen and elastin that is not visible and happens even before you sunburn. These types of damage can occur without sunburning. So you can’t measure all the damage done to your skin by only being concerned about sunburn.
So let’s talk about an important difference between sunscreens that you should know about.
Physical Sunscreens
Physical Sunscreens contain active mineral ingredients, such as titanium dioxide or zinc oxide, which work by sitting on top of the skin to deflect and scatter damaging UV rays away from the skin. They are often referred to as physical blockers.
Pros of Physical Sunscreen:
Offers protection against both UVA and UVB rays and is naturally broad spectrum
Protects from the sun as soon as it’s applied, no wait needed
Lasts longer when in direct UV light (but not when doing physical activities that cause the skin to get wet or sweat)
Less likely to cause a stinging irritation on the skin, making it better for sensitive skin
Better for those with heat-activated skin(such as rosacea and redness) since it deflects the heat and energy given off by the sun away from the skin
Less likely to be pore-clogging, making it ideal for acne-prone skin
Longer shelf life
Cons of Physical Sunscreens:
Can rub off, sweat off and rinse off easily, meaning more frequent re-application when outdoors as needed
May leave a white-ish cast on the skin, making some formulas incompatible for medium to dark skin tones
Can be less protective if not applied and re-applied generously and accurately since UV light can get between the sunscreen molecules and get into the skin
CHEMICAL SUNSCREENS
Chemical Sunscreens contain organic (carbon based) compounds, such as oxybenzone, octinoxate, octisalate and avobenzone, which create a chemical reaction and work by changing UV rays into heat, then releasing that heat from the skin. They are often referred to as chemical or organic absorbers.
Pros of Chemical Sunscreens:
Less is needed to protect the skin because there is no risk of spaces between the sunscreen molecules after application
Tends to be thinner and therefore, spreads more easily on the skin.
Cons of Chemical Sunscreens:
Can possibly cause and increase in existing brown spots and discoloration due to a higher internal skin temperature ( over-heated skin can make brown spots worse, such as melasma)
Requires about 20 minutes after application before it starts to work
Increased chance of irritation and stinging (especially for those who have dry skin with a damaged moisture barrier) due to the multiple ingredients combined in order to achieve broad spectrum UVA and UVB protection
The higher the SPF (such as formulas of SPF 50 or greater), the higher the risk of irritation for sensitive skin types
The protection it offers gets used up more quickly when in direct UV light, so re-application must be more frequent.
Increased chance of redness for rosacea-prone skin types because it changes UV rays into heat which can exacerbate flushing
May clog pores for oily skin types
So what is our preference, we more often than not recommend physical sunscreens to our clients.