Summertime, and it’s time we talk sunscreen. As a dermatologist, this is something I discuss with my patients all the time. If you’ve been in the office, I’m sure you’ve heard me say that using sunscreen of at least SPF 30 everyday—rain or shine, summer or winter—is extremely important.
About UVA/UVB rays
The sunlight that reaches us is made up of two types of harmful rays: long wave ultraviolet (UVA), and short wave ultraviolet (UVB).
- UVA rays penetrate deep into the dermis, the skin’s thickest layer, and are a threat to the skin.
- UVB rays are the ones that burn the superficial layers of your skin and cause sunburns.
The importance of blocking UVA and UVB rays
Regardless of the weather or the time of year, UVA and UVB rays reaching your skin increase your risk of skin cancer and cause photoaging. Even if you aren’t concerned about skin cancer, which you should be, sun exposure ages skin, and not in a good way. Sun exposure causes brown spots, wrinkles, and sagging leathery skin.
Sunscreen is your shield and helps block those rays and protects your skin. Sun Protection Factor (SPF) is a relative measure of how long a sunscreen will protect you.
I’m often asked how high an SPF should a person use. To answer that, it’s important to understand what SPF does. Basically, it measures how much longer it takes your skin to redden when wearing SPF rated sunscreen verses without SPF sunscreen.
For example, if it takes 20 minutes in the sun for your skin to redden, using an SPF 30 would protect your skin from reddening 30 times that.
So, how much of the sun’s rays are the various SPF sunscreen’s blocking?
- SPF 15 blocks about 93%
- SPF 30 blocks about 97%
- SPF 50 blocks about 98%
Use a sunscreen with SPF 30 and above to be safe. And, remember to check the expiration date on your sunscreen. If it’s expired, throw it out and buy anew.
It only works if you use it
This may sound obvious, but sunscreen only works when you use it, and it needs to be applied often. If you go in the sun, you need to reapply sunscreen every couple of hours. And, if you swim or play in the water, always reapply after drying off. Remember those easy-to-miss places, such as behind the ears and your neck.
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