Spring is beginning to bloom and summer is right around the corner! We’re looking forward to bright sunny days ahead. That being said - now is the perfect time to talk about the importance of sunscreen (although it is also important to wear sunscreen in the winter, too). We’re here to answer all the questions you may have about sunscreen/SPF.
What Does Sunscreen Protect You From?
There are two types of UV light that can harm your skin - UVA, and UVB.
UVA rays are absorbed deeper in the skin and cause premature skin aging, wrinkling, and age spots. Fact: UVA rays are not blocked by glass (windows or car windshield!)
UVB rays are absorbed more superficially and cause the skin to burn. Fact: UVB rays are blocked by glass.
Skin cancer risk and premature aging are increased by cumulative exposure to both. The best sunscreen is a broad spectrum that protects against both UVA and UVB.
What Does SPF Mean?
SPF stands for Sun Protection Factor. SPF is a relative measure of the amount of time sunscreen will protect you from burning when exposed to UV rays, specifically UVB rays. For example, if you burn after 10 mins of being in the sun, applying an SPF 30 you could technically spend 300 mins (30 times longer) in the sun before burning. But It’s only a technical measure! A single application of sunscreen will not last on the skin for this amount of time. It rubs off our skin, we sweat it out and it’s only water-resistant.
Sunscreen should be reapplied every three to four hours if you’re sweating or wiping your skin, and every forty or eighty minutes if you’re in the water.
What Are Chemical vs Mineral Sunscreens?
Mineral or Physical Sunscreens:
- Contain active ingredients zinc oxide and/or titanium dioxide
- Block both UVA and UVB
- Act like a physical barrier that blocks the light and reflects it off
- These are less irritating but can also leave a white cast
- But thankfully with the use of vet small minerals (nanoparticles), you can find mineral sunscreens that won’t leave a cast even on darker skin types (like ours!)
- Contain one or more of the following active ingredients: avobenzone, oxybenzone, octisalate, octocrylene, homosalate, and octinoxate
- They act like a sponge by absorbing the light, converting it to heat, which radiates away
- Some may not block both UVA and UVB
- It may be irritating to sensitive skin and for some can make the eyes sting and water
What Is The Best Sunscreen?
Sunscreen is regulated and has to be approved by US FDA and Health Canada before being sold in the US and Canada respectively.
The best sunscreen is one that is broad-spectrum, meaning it protects against both UVA and UVB, SPF 30 or higher, and the one YOU will use regularly!
Does Sunscreen Prevent Skin Damage/Aging/Wrinkles?
There is strong evidence to show that regular, daily use of sunscreen protects against photoaging, including fine lines and pigmentation changes.
You might be thinking, I don't need to use sunscreen daily… I don’t get a lot of sun exposure, I’m not a sunbather… Or, I wear sunscreen while I’m on vacation, I don’t get a lot of sun otherwise.
All-day sun exposure or while on a sunny beach vacation is called intense exposure. But our greatest exposure to UV rays is incidental. Meaning, it’s the sun exposure we get while driving our cars (UVA rays), walking to our cars, waiting for the bus, walking to the mailbox, shoveling the snow, etc. It’s the cumulative exposure of intense and incidental sun exposure that matters.
Cumulative UV exposure is a major contributor to aging skin through the formation of radical oxygen species that leads to oxidative stress and DNA damage. One study looked at the activity changes of genes that are linked to aging in the skin after UVA exposure. They compared unprotected skin to skin protected by sunscreen and found sunscreen protected skin had lower activity of genes linked to aging.
Daily use of sunscreen is significantly more effective than intermittent use of equal or high SPF products. A randomized controlled trial done in Australia showed that daily use of sunscreen showed no detectable increase in skin aging after 4.5 years compared to discretionary use.
High SPF products account for the underuse of sunscreen but these high SPF products still need to be used daily and reapplied regularly.
Does Sunscreen Prevent Skin Cancer?
Skin cancer is the most common form of cancer. Its incidence will continue to rise in the coming decades due to an aging population. Sunscreen use is so important as most skin cancers are preventable by reducing UV exposure.
A randomized controlled trial done in Australia found a 40% significant decrease in squamous cell carcinoma rate in those with daily use of sunscreen compared to discretionary use. There have been many other studies that have shown a significant decrease in rates of melanoma, basal cell carcinoma, and actinic keratoses.
How To Apply Sunscreen
As dermatologists, we strongly advise everyone to practice sun safety including the use of a broad-spectrum sunscreen with at least SPF > 30 in all exposed areas and all year round.
- Apply to dry skin 15 mins before going outside.
- It should be reapplied every three to four hours or more frequently if outdoors or after swimming or sweating (check directions on the bottle).
- For most adults, about 1 ounce (enough to fill a shot glass) is required to cover the body
- Roughly a quarter teaspoon is required to cover the face.
- Be sure to apply to your neck, ears, tops of your hands, and tops of feet.
- Don’t forget your lips! There are lip balms available that contain sunscreen with > SPF 30.