Sun protection is more confusing than ever. Like, what’s the difference between SPF 15 or 30, and how much do you really need? How often do you really need to reapply? What if you’re inside all day or wearing UV protective clothing? 

Because sun protection should play a key role in everyone’s skincare routine, we’re happy to share expert answers to each of these questions. After all, practicing sun safety with a good SPF* can help protect you from skin cancer, slow down signs of aging, reduce chances of developing hyperpigmentation, and help prevent dreaded sunburns (which, yes, can still happen on a cloudy day).

What is SPF?

Before diving into what SPF means, it’s important to understand the difference between UVA and UVB rays. UVA rays penetrate the deeper layers of the skin and are the main factor in photoaging and wrinkles, while UVB rays are the main culprit for sunburn. Research has linked both UVA and UVB rays to skin cancer.¹ 

SPF stands for “sun protection factor” and measures how much UV radiation is required to produce sunburn on skin protected with sunscreen relative to the amount of UV radiation required to sunburn unprotected skin. As the SPF value increases, sunburn protection increases.²

Why is SPF so important?

There’s a big misconception that SPF relates to how much time you can stay in the sun. SPF relates to the amount of sun exposure you’re protected against, not the amount of time you’re exposed to the sun. SPF 30 will protect you 30 times more than wearing no sunscreen at all. That doesn’t mean it will last twice as long as SPF 15 (or half as long as SPF 60).

What does PA mean?

You might also see the label “PA” on your sunscreen’s packaging. PA is short for the protection grade of UVA. It’s a Japanese rating system measuring the effectiveness of blocking UVA rays, while an SPF rating most specifically applies to UVB rays. The PA rating can have up to four “plus” (+) signs.

In the United States, sunscreens are regulated by the Food and Drug Administration, which considers sunscreens that pass the broad-spectrum test to protect from both UVA and UVB rays,³ even without a PA grade. Because of the ambiguity of the PA rating system, Curology keeps it simple by sticking to the conventional SPF system, creating a broad-spectrum sunscreen to keep you protected. 

Why are there different SPF levels?

SPF was introduced in the 1970s to educate consumers about the amount of sun protection they receive from their sunscreen. In September 2021, the FDA released new regulations requiring a skin cancer and skin-aging alert for sunscreens with SPF values over 2 but less than 15.⁴ Higher SPF sunscreen provides more sunburn protection. Those with SPF 30 and higher are better equipped to protect themselves from sun damage that can cause skin cancer and early signs of aging.

No matter what SPF you choose, its effectiveness begins to wear off after application (yes, even that SPF 100). That means you need to reapply sunscreen every two hours or after you’ve toweled off from excessive sweating or swimming. Besides avoiding the sun, sunscreen is your best defense against sun damage.

What is the difference between SPF 15 and SPF 30?

Sunscreens must pass FDA-approved testing to make an SPF claim, and that testing uses complicated formulas to determine SPF values. SPF 15 protects you from about 93% of UVB rays, while SPF 30 protects you from about 97%. In other words, SPF 15 allows about 7% of rays through while SPF 30 allows about 3%.

When you’re comparing SPF 15 vs. 30 for the face, you’re better off going with SPF 30. It’s what the American Academy of Dermatology and other experts in the field recommend.⁵ Acne can also contribute to your decision of which sunscreen product to use, as some products may be comedogenic. A sunscreen that’s designed for oily, acne-prone skin (like Curology’s!) can help to keep your skin safe from sun damage, while also reducing the likelihood of making breakouts worse. 

When deciding between SPF 15 and 30, you should consider your skin type, where you live, and what time of day you’ll be in the sun. SPF 30 and above is the choice recommended by experts! And remember, there is no such thing as safe tanning. Curology providers advise against tanning, whether outdoors or in a tanning bed.

What’s better: SPF 15 or 30 for Black skin? 

Darker skin may have some natural SPF protection, but it’s not enough to forgo sunscreen.⁶ Although melanoma is less prevalent in those with black skin, this demographic often faces a worse prognosis when they are diagnosed with this kind of skin cancer.⁷ The American Academy of Dermatology recommends a minimum of SPF 30, regardless of skin color. 

What if I'm staying indoors?

You need to wear sunscreen indoors, especially if you enjoy basking in the heat by the window. More than 50% of UVA light penetrates the glass.⁸ Sunscreen with an SPF 30 or higher works for everyday use with occasional sun exposure, like grabbing a coffee with friends, driving, or walking the dog. Make sure you purchase a broad-spectrum sunscreen to protect against both UVA and UVB rays and reapply every two hours when you have prolonged exposure. 

Does a sunscreen with a high SPF protect skin better than a lower SPF?

Higher SPF-rated sunscreens may give people a false sense of security. Remember, the SPF value refers to the amount of protection, not the time. For example, if applied correctly, SPF 30 protects you from 97% of UV rays whereas SPF 50 protects you from 98% of UV rays.⁹ No matter the strength of SPF, you still need to reapply enough sunscreen using a tactic like the two-finger rule to protect yourself from skin damage. 

To protect yourself from both UVA and UVB rays, you need to use a broad-spectrum sunscreen. Another result of recent FDA regs requires transparency in labeling, so if a sunscreen hasn’t undergone broad-spectrum testing, the manufacturer can’t mislead consumers through labeling. 

5 tips to get the most protection from your sunscreen

Hopefully, you now better understand what SPF means, the differences between the values, and why it’s so important to wear a broad-spectrum sunscreen—not just during summer, but year-round. Every morning, always remember to don some sunscreen. Your skin will thank you for it!

Here are a few bonus tips to get the most from your sunscreen: 

• Use SPF 30 or higher whether you’re staying in or going outside 

• Apply sunscreen about 15 minutes before going outside—even on cloudy days

• Reapply sunscreen every two hours or after sweating or swimming

• When swimming or being active outside, use a water-resistant sunscreen

• Use the right sunscreen for your skin type

Sunscreen formulated to work with your skincare products

The sunscreen by Curology is a 100% mineral-based, grease-free sunscreen that won’t leave a white cast on your skin or clog your pores. Developed and tested by dermatologists, the sunscreen was formulated specifically with acne-prone skin in mind. The broad-spectrum sunscreen uses zinc oxide to block UV rays and protect you from the sun. An SPF 30 sunscreen is formulated to work synergistically with Curology products and can be used daily as part of your skincare routine.

Get your personalized skincare routine with Curology

Get your personalized skincare routine with Curology

Start your skin quiz

The sunscreen is available through a Curology subscription only, but new members can sign up for a 30-day trial and add the sunscreen to their order for free (just pay $4.95 to cover shipping). Existing members can add sunscreen to their plan for $14 (plus taxes where applicable). 

P.S. We did the homework so you don’t have to:

1. Latha, MS., et al. Sunscreening Agents. Journal of Aesthetic Dermatology. January 2013.

2. U.S. Food and Drug Administration. Sun Protection Factor (SPF). (n.d.)

3. U.S. Food and Drug Administration. Sunscreen: How to Help Protect Your Skin from the Sun. (n.d.).

4. U.S. Food and Drug Administration. OTC Monograph M020. (September 2021). 

5. American Academy of Dermatology. Sunscreen FAQS. (n.d.). 

6. Cestari T, Buster K. Photoprotection in specific populations: Children and people of color. J Am Acad Dermatol. (2017, March).

7. Mehendraraj, K, et al. Malignant Melanoma in African-Amerians. Medicine. (April 2017). 

8. Venosa A. 5 Sneaky Ways You’re Being Exposed to the Sun’s UV Rays. Sun & Skin News. (2017, May 10).

9. Dale Wilson, B., et al. Comprehensive review of ultraviolet radiation and the current status on sunscreens. The Journal of clinical and aesthetic dermatology. (2012).

*Sunscreen cannot prevent all harm from UV rays.

* Subject to consultation. Subscription is required. Results may vary. 

Written by

Curology Team