Sun protection factor (SPF) is a rating system introduced in 1974 and measures how much UVB radiation is needed before a sunburn shows up on protected skin relative to the amount of UVB radiation required to produce sunburn on unprotected skin. As the SPF value increases, sunburn protection increases.
SPF relates ONLY to effects on UVB rays. It has nothing to do with effectiveness against UVA rays, the ones which cause damage below the skin's surface.
In short, SPF measures how long a sunscreen will protect you from UVB rays — the rays that cause sunburn and the outer layers of the skin (the epidermis).
Here's some quick background on SPF before we answer the question, "What SPF do I need?”
SPF Speaks to Surface-Level Skin
First, SPF refers to the protection of the skin's outer surface only. The sun protection factor measures the amount of UVB rays that reach the top layers of skin. It does not measure the protection of UVA rays, which go into deeper skin layers.
High SPF sunscreens overpromise sun protection, give a false sense of security, overexpose people to UVA rays deeper into skin layers and thus raise their risk of cancer.
In other words, high SPF sunscreen formulations can protect the skin surface more than it protects lower skin layers, producing a disconnect between surface effects (redness and tightness) and damage below. This is one reason why skin cancer continues to increase even though Americans buy more and more sunscreen. (Not to mention petrochemicals, but that's a whole other story.)
SPF is Often Overstated
Second, many formulations overstate SPF, as the testing for SPF is ripe for gaming, where manufacturers add anti-inflammatory ingredients, which thwart the skin's natural red reaction, thereby creating the impression that damage is not occurring, while it actually is occurring, especially in deeper layers.
Many studies have found that people are misled by the claims on high-SPF sunscreen bottles. People assume the high SPF number on the sunscreen bottle means they can stay in the sunshine longer and not need to reapply as often. This is a mistake and those people are getting more UV damage than they realize.
Diminishing Return on SPF
Third, there is a diminishing return on SPF protection. An SPF of 30 blocks 97% of the UVB rays hitting your skin. An SPF of 50 blocks 98% of the UVB rays. For example, a person using a 30 who gets 4 hours of sun will receive 240 minutes / 30 = 8 equivalent minutes of UV effects, while another using a 50 will receive 240/50 = 4.8 minutes. This is a minuscule difference.
All that being said, at Waxhead, we are considering the development of a 50 SPF line, but as yet, we have not found the right formula which will protect BOTH the surface and deeper tissues at roughly the same level (to avoid the above disconnect).
Until then, our highest SPF is 35, delivered by our Vitamin D enhanced sunscreen. As most of our sunscreens, it's thick and tough and takes a bit of time to apply and spread, but once it's on, it stays on through the wind, water, sweat, and surf, as well or better than any other product, (all while actually NOURISHING skin instead of loading it with dangerous petrochemicals).
Another product you might like is our natural sunscreen stick. It's the thickest one we make with a 30 SPF. This formulation is the same as our sunscreen tins, just with a different application method (pushup stick). The tin is included in our sample pack, which you might like to try first, as it gives you a great idea of several of our products.
What SPF do I need?
We recommend a sunscreen with an SPF rating of 30-35, and if you're considering something higher, make sure it doesn't have one or more of the above issues. Better yet, send us a link, and we'll be more than happy to review its ingredients in detail and give you our honest evaluation. It may be that someone's developed an honest-to-goodness validly safe high SPF product, and we are absolutely interested in learning about that!
Also, look for the words “Broad Spectrum” — this helps make sure you’re protecting yourself from UVA rays (as well as UVB rays). Make sure it contains NO petrochemicals, and that it either uses only non-nano zinc oxide as an active ingredient (at least 20%, but 25% is best) and that if it contains no more than 5% titanium dioxide. Always read the active and non-active ingredient list to make sure you’re not putting harmful chemicals on your skin.
And please remember your hat, sunglasses and long sleeve shirt — for those especially long days on the boat or at the beach.
NEXT STEPS
1. Know your ingredients — Flip over your sunscreen and read the ingredients. We want everyone to know what good ingredients are, regardless of whether they use our products or not. Your health is worth it.
2. Buy safe sunscreen — Waxhead is dedicated to using only the healthiest, safest, most effective ingredients in our sunscreens. Shop Safe Sunscreen here.
3. Teach a friend — If you know someone who might still be buying sunscreen with questionable ingredients, please share this post with him/her.
Sources
https://www.ewg.org/sunscreen/report/whats-wrong-with-high-spf
https://www.skincancer.org/blog/ask-the-expert-does-a-high-spf-protect-my-skin-better
https://www.fda.gov/about-fda/center-drug-evaluation-and-research-cder/sun-protection-factor-spf
