Table of Contents • Note: if this is a members-only article, some sections may only be available to Premium or Unlimited Members.
- Introduction
- To what extent do people use sunscreen?
- How does sunscreen work?
- What is the sun protection factor (SPF)?
- Misconceptions about SPF
- Should I wear sunscreen stronger than 50 SPF?
- How safe are sunscreen ingredients?
- Table 1: Proposed Categories for Sunscreens (FDA)
- Other Adverse Effects of Sunscreens
- Are mineral sunscreens effective?
- What are the “Best” Sunscreens?
- What about “natural” sunscreen products?
- What is UPF clothing?
- Sun Protection Best Practices for Backpackers
- References
- Related Content
Introduction
Sunscreen for hiking and backpacking tends to take a back seat to other (more prominent) types of outdoor gear. While sunscreen use is prevalent in our society, there are basic facts about sunscreen that may not be known by the general public. The purpose of this article is to provide information to enable users to safely and effectively use sunscreen while adventuring.
As a long-time hiker and backpacker, I’ve grown wary of the harmful effects of ultraviolet light. Our adventures often take us to places with generous sun exposure. Higher altitudes mean less atmosphere to run interference on those UV rays hitting your skin, and locations with water and snow increase your exposure due to the amount of reflection from their surfaces. As a pharmacist and academic, I was deeply curious to understand how sunscreens work, learn about the safety and efficacy data behind their active ingredients, and understand the recommendations for their use.
This research review is the outcome of a deep dive into several academic papers surrounding the issue. In addition, I will close with a summary of what I believe are best practices that backpackers can follow to sufficiently and safely protect themselves from the sun. I hope this review provides some insight into how to choose and use sunscreen for hiking and backpacking.
To what extent do people use sunscreen?
When applying sunscreen for hiking, most users probably err on the side of not applying enough, or often enough.
My zealous application of sunscreen seems to make me an outlier: one survey conducted among thousands of US adults showed that a mere 14.3% of male respondents regularly used sunscreen on the face and other exposed skin. Women had about twice the rate of use, at 29.9%. Men have room to grow in this practice – over 40% stated that they never used sunscreen on the face or skin (again, compared to women at approximately 27%)1.
When looking at facial application, about 27% of respondents stated they were using sunscreen with SPF 50 or higher.
How does sunscreen work?
Sunscreens use organic and inorganic molecules to prevent ultraviolet radiation from reaching the skin. Their mechanisms of action fall into two general categories: physical filters and chemical filters.
Physical filters work by scattering ultraviolet radiation and providing a physical barrier covering the skin, as shown here and here.2,3
On the other hand, chemical filters operate by absorbing short-wavelength ultraviolet radiation and converting them into thermal energy.
Some sunscreens contain both types of filters.
What is the sun protection factor (SPF)?
Ultraviolet radiation is often then categorized by wavelength, the most frequently referenced wavelengths being UVA1 (300-400 nm), UVA2 (315-340 nm), and UVB (280-315 nm).3
Approximately 95% of the ultraviolet radiation that reaches the earth’s surface is UVA. 5% is UVB. Thanks to the ozone layer, about 90% of UVB never even reaches us.3,4
While UVA tends to be constant throughout the day, UVB has a peak, typically around midday. UVA penetrates deeper into the skin and causes more photoaging and carcinogenesis, while UVB is less deeply absorbed and has a greater impact on tanning and sunburn.3
UVB filtration is important because UVB is responsible for most biological effects such as sunburn, pigmentation, synthesis of vitamin D3, and cancer formation. When considering SPF protection from UVB, SPF 15 filters 93% of UVB rays, SPF 30 filters 97%, and SPF 50 filters 98%. 2 Sunscreens that also protect against ultraviolet radiation in the longer wavelength UVA spectrum are termed “broad-spectrum.”
Misconceptions about SPF
A common misconception is that the sun protection factor (SPF) is multiplicative. In other words, SPF 30 is not twice as strong as SPF 15.5
Another misconception is that SPF correlates to the amount of time exposed to the sun. For example, “if it takes you 10 minutes to burn without sunscreen, then using a sunscreen with SPF 15 means it takes you 15 times longer to burn, or 150 minutes” is a misleading and incomplete statement.
The FDA clarifies that SPF is more related to the amount of solar exposure rather than solar exposure, impacted by factors such as the time of day, skin type, altitude, global location, and the amount and frequency of sunscreen that is applied. In other words, according to the FDA, “SPF does not inform consumers about the time that can be spent in the sun without getting sunburn. Rather, SPF is a relative measure of the amount of sunburn protection provided by sunscreens.”6
Should I wear sunscreen stronger than 50 SPF?
Is there an SPF above which you start getting diminishing returns?
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Discussion
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Companion forum thread to: Sunscreen for Hiking and Backpacking: Efficacy, Ingredient Safety, and Best Practices
Dan Hu reviews current research regarding the safety and efficacy of sunscreen for hiking and backpacking, including ingredient efficacy, safety, and best practices for outdoor adventuring.
Nice summary. On “best practices” I second the “clothing” option when backpacking. Not only do you save weight on longer trips, but it is much easier to stay clean. When it’s dusty I find dirty sticking to wherever I applied sunscreen and it’s a pain to get clean at the end of the day.
There is an organization that analyzes the chemicals in everything from Sunscreen, to laundry products etc and rates them as to their efficacy and chemical safety and impact on the environment which is more and more being seen in oceans and rivers.  It is Environmental Working Group.  And their most “A”rated products are EWG verified.  You many want to check it out.  I found I like the Attitude products—especially their sunscreen.
And if you swim in the lakes or streams, the sun screen ends up in the water… can’t be good for the critters…
Yeah, EWG does good report on sunscreens
https://www.ewg.org/sunscreen/
I’ve tried zinc and titanium, but I didn’t like it because it comes off and gets on my clothes creating a bit of a mess.
I use long pants, shirt, wide brimmed hat. Sometimes I’ll put sunscreen on my neck and back of hands that aren’t covered.
and if you don’t like EWG, there’s Consumer Reports
https://www.consumerreports.org/cro/sunscreens.htm
Daniel, thanks for pulling this information together. And Jane & Jerry, thanks for the lead to EWG. Having just had my dermatologist take off yet another suspicious piece of sun damage, it’s relevant.
+1 to clothing, although I still use some sunscreen on my face. Sticks are less hassle for me.
“+1 to clothing, although I still use some sunscreen on my face. ”
Yep to all that. I cover up good at altitude, where the effects of sun on the skin is exacerbated because of a thinner atmosphere. counter intuitively, thin SPF material can be cooler than leaving your skin bare to the sun/elements. And it protects against bugs and brush as well. I wear a broad brimmed hat for sure. And I use a little sunscreen as well. Sun reflects wildly off snow, as we know. Ditto, water and rock.
Nice article. Only 2 of the 10 guys I regularly go out with use sunscreen, not counting myself.
In my 20’s I was out a lot and used sunscreen semi regularly. Now in my 30’s I prefer long pants, long shirt, sun gloves, with a wide brim (4″) full brim hat, and on 90% of my hikes use the solar umbrella for comfort (greatly reduces sweating in direct sun and high temps). This only leaves my face and neck partially exposed and I apply sun screen to these areas usually once in the morning, or during peak sun morning and lunch.
I went to long clothing+limited sunscreen over short clothing + extensive sunscreen for a few reasons –
-Sunscreen does not prevent skin aging. Even if you religiously apply you will eventually get leatherly skin.
-Skin cancer in my family. Clothes work much better and more reliably than screen
-A light colored sun shirt is cooler than no shirt most of the time, and can be wetted for even better cooling
-Every plant around me is itchy, spiky, or generally unpleasant to brush by. Long clothing prevents a lot of scrapes and itching
-Mites love me. Even with long, permethrin treated clothing I get a few bites. Without it im just a walking mite buffet which is extremely itchy and requires permethrin lotion to fix, which I’d like to avoid.
I dunno how safe it is but I’ve used Neutrogena sunscreen in various SPFs since it first came out and like it. But then I only use it 3 times a week, not every day.
Eric, I’ll second your suggestion of the Neutrogena. I think I found a bottle of my daughter’s old sunscreen, because it’s a brand a bit fancy for my taste, but it has a very nice nonstick/matte finish once it has been applied. Maybe a little prissy for backpacking, but excellent if you are going to have your photo taken e.g. at an outdoor wedding!
For Australian sun, sunscreen is essential on exposed parts, and sometimes it is just too unpleasant to wear long pants and long shirt. Areas like face and neck, and also back of hands need sunscreen applying. If you walk anywhere along the beach, don’t forget the backs of the feet. You don’t have to have had many episodes of sunburn to the top of your foot, to realise how difficult it is then to get a shoe on. I’ve also seen some spectacular burns around the Achilles tendon when people forgot that their sunscreen only went down as far as their socks, removing their boots for the beach walk.
Winter or summer I carry a lipstick sunscreen in my pants zip pocket, and reapply frequently. Blistex brand tastes best, some are awful. It also gets on your bite valve or bottle mouth, so pick a nice flavour.
Vitamin D is a genuine concern. My father died of skin cancer aged 59, and my little brother got a melanoma in his 40s. I have been very careful about the sun for over 40 years, and managed to get vitamin D deficiency. But 1 tiny capsule a week is nothing compared to a blast of liquid nitrogen. For those who haven’t had the pleasure, my dermatologist said that it would feel like being hit over the head with a hammer. The initial freeze wasn’t too bad, but as it started to thaw, I knew what he meant. We’ve repeated that fun scenario twice a year, for 30 years…
Remember that water and snow reflect UV, so take extra care with that lunch stop/swim break with ‘air-drying’ in the sun. Many sunscreens are marketed as ‘sport’ or paradoxically, ‘toddler’ and have a 4hr reapplication time. They have a higher concentration of active ingredients, with more zinc/titanium oxide in the toddler versions.
Marcus, sunscreen does decrease skin ageing, you’ll look younger than your walking mates who don’t wear it. But backpacking is still more sun exposure than accountancy, so you and I look more like farmers than vampires!
Vitamin D- The reference range was set for decades and deficiency was not common. Somewhere around year 2000 some “researchers” start putting out medical reports of benefits of higher vitamin D levels (a lie). The reference range gets moved higher so more people are now told they are deficient. It took years (10-15+) before reports found no real value of higher levels. I saw it as a scam that drove up healthcare costs…end of rant.
Does anyone have “mineral sunscreen” they actually like? (Anyone else feel like this is just rebranded sunblock?)
I picked some up on accident at REI. Worst decision ever. At the interface with my clothes, it rubbed off and I was burned. Wading through streams 3 hours after application (way longer than recommended), the “grease” (beeswax, oil, whatever keeps the zinc oxide in suspension) created a sheen on the water. This same grease allowed dirt to cling like no other.
After 5 days, I used my hiking shirt to scrape it off before I got in the car. I put that shirt through the laundry at least times before I gave up, permanently ruined.
I’m glad this article made it clear that stopping the burn (UVB) and stopping cancer (UVA) are two different goals and I’m probably slacking on the latter, but I don’t currently see options other than going back to long clothes, which have their own drawbacks.,
I could not read the article but I was thinking of trying ‘Reef safe’ type sunscreens – with the hope they would be safe for river and lake life also.
Just returned from 3 days walking in Mont Bell Wikron ‘Parka’. It’s t-shirt material (thin polyester) with hood, long sleeves/thumbloops and full zip. Very comfortable at 11-20 degrees Centigrade, steamy weather with intermittent full sun.
Easier than sunscreen and probably being able to intermittently open the zip (when shaded) made up for the arms being a bit warmer. And the hood pulled on at night for mosquitos/warmth.
SOL sun screen is my favorite.
I was selling a used HP laser printer years ago, and the guy who bought it from me was founding this new company (“Sol”) and he gave me a sample. I have been using it ever since.
I was hoping for some advice how to avoid having your eyes burn while at the same time apply sunscreen (not cloth / hat which is hot) above eye level…
I have been using Z Blok sunscreen for years. Very little eye irritation on application or from perspiration. Zinc, but it rubs in and leaves very little white skin.
Indrit, the SOL sunscreen does not bother eyes at all. When the companies founder showed me the sunscreen, he purposely put it right into his eye to demonstrate. No sting.
For me, it is important to buy a sunscreen I want to use (smell, ease of application, etc). Like others, have had slices of my face/head removed of pre-cancerous stuff. Not happy with the application or look of the mineral-based formulas. I am fine using non-mineral sunscreens even with the uncertainty of risk of some of the ingredients. Never heard of anybody dying from too much sunscreen but have lost some friends to skin cancer at early ages. I also started to wear more sun-appropriate clothing to minimize the amount of sunscreen I need to use. Just ordered my summer allotment from Walmart based on the latest consumer reports … Equate Ultra lotion (every day face usage) and Australian Gold Spray (when I just wear swimtrunks river/lake kayaking )
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