Q: What are key factors to consider when selecting and using sunscreen?
A. In brief:
- For prolonged outdoor activity (4+ hours of sun exposure), choose a sunscreen that offers a sun protection factor (SPF) of 30 or higher.
- Choose a sunscreen effective against both ultraviolet-A and ultraviolet-B (UVA and UVB) light, typically identified as a "broad-spectrum" sunscreen.
- Be aware that an SPF number only indicates a sunscreen's effectiveness against UVB rays (the UV light that can burn skin). So far no rating system exists for UVA rays (which cause skin to age and wrinkle). To shield your skin from both UVA and UVB rays, look for sunscreen ingredients that the U.S. Food and Drug Administration has identified as providing broad-spectrum UV protection.
- Apply sunscreen generously (for adult bodies, use 1 ounce per application; enough to fill a shot glass). Spreading too thin a layer likely means your skin will not get the sunscreen's intended protection.
- Shade and protective clothing are other methods skin-care professional recommend for shielding skin from UV light.
Those are basics of sunscreen. If you're a casual shopper, this might be all the information you need. The remainder of this article takes a more in-depth look at the finer details of sunscreen and ultraviolet light. It's useful information we think many readers will find informative.
UV Light and Skin Health
Q: Why should I be concerned about sunlight?
A. Sunlight travels in waves and includes both visible light and invisible ultraviolet (UV) radiation. Visible and UV light sit adjacent to one another on the electromagnetic spectrum. This spectrum includes other forms of radiation, from radio waves and microwaves to X-rays and gamma rays.
Visible light waves range in length between 400 and 700 nanometers (nm); the shortest wavelength of visible light yields the color violet (400-420 nm). Ultraviolet light, meanwhile, travels in even shorter waves that range between 200 and 400 nm. A nanometer is one-billionth of a meter.
UV radiation is divided into 3 categories: UVA, UVB and UVC rays.
- UVA rays (320-400 nm) penetrate skin deeply, causing aging, wrinkles and potentially skin cancer.
- UVB rays (290-320 nm) are sunburn-causing solar rays; they can also contribute to skin cancer.
- UVC rays (200-290 nm) are absorbed by gases in the earth's atmosphere, which is a good thing, since UVC rays are considered potentially deadly to humans.
The American Cancer Society reports that more than 1 million non-melanoma cases of skin cancer diagnosed annually in the U.S. are sun-related. UV light can also weaken the body's immune system.
UVA light presents a subtle threat to our skin. Unlike a UVB-caused sunburn, it creates no discomfort and its impact (wrinkles and other signs of premature aging) may not become apparent for years. Consider:
- Because they're slightly more elongated than squiggly UVB rays, UVA light can more effectively penetrate clouds and impact your skin. Still, UVB rays are a threat to cause sunburn on days with overcast or thinly clouded skies, and some data suggest UVB light is a danger even on days with thicker cloud cover.
- UVA rays have the capacity to impact skin during any daylight hour. (UVB rays do most of their damage between 10am and 4pm.)
- UVA rays, unlike UVB light, can also penetrate through most glass. As a result, your skin won't get burned by sunlight coming through a window, but you could be at risk for accelerated aging.
For these reasons, some people include sunscreen in their daily cosmetic routine.
Sunlight can benefit the body by helping it synthesize vitamin D. However, numerous skin care authorities and cancer-prevention agencies counter that humans can meet their vitamin D needs through diet.
Q: What's the best way to protect my skin?
A. Many voices in cancer-prevention communities advocate the use of skin-shielding clothing (wide-brimmed, neck-covering headwear; full-length pants; loose-fitting, long-sleeve shirts) as an outdoor person's primary protection. Sunscreen, while important, should be a second line of defense.
Lightweight outdoor clothing today often carries a rating—an ultraviolet protection factor (UPF) rating. Such clothing uses a denser weave, darker colors or an applied treatment to block UV rays. Ratings go as high as UPF 50+. A white cotton T-shirt offers a UPF between 4 and 8. When wet, it provides less protection.
Learn more about the benefits of sun-shielding clothing and the ultraviolet protection factor (UPF) ratings attached to such garments in the REI Expert Advice article
Understanding Sun Protection Clothing.
Q: What does a sunscreen's SPF tell me? Which number is best?
A. Higher SPF (sun protection factor) numbers indicate better protection against sunburn-causing UVB rays. They offer no indication, however, of UVA protrection. The following chart compares the benefits of 2 SPF ratings popular among active outdoor people:
| SPF Against UVB Rays | % of UVB Rays Absorbed | Considerations |
| SPF 30 | 97% | Excellent general-purpose sunscreen for all activities and conditions. Contains fewer sun-blocking agents than higher SPF sunscreens, so skin can breathe and perspire more freely. |
| SPF 50 | 98% | Good for extended high-elevations exposure, thin-skin body regions (nose, ears) and children. Includes a high quantity of sun-blocking agents; may feel heavy, greasy, or warm on skin and reduce its breathability. |
The SPF number on a sunscreen label is typically between 2 and 50. In a laboratory setting, SPF 30 sunscreen absorbs roughly 97% of UVB rays; SPF 15 absorbs about 93%. Yet several real-world factors (perspiration and activity level, your location on the planet, your proximity to light-reflecting water or sand, the time of day) may alter that percentage.
In general, SPF 30 is regarded as a good, all-purpose sunscreen for active people who spend extended time outdoors. Dermatologists commonly recommend a SPF of no less than 15, though 30 is widely accepted as a smart choice for active people who routinely stay outdoors for long periods.
SPF numbers do not indicate the duration of a sunscreen's protection. (This is a common misconception about SPF.) For example, wearing SPF 15 sunscreen does NOT mean your skin can withstand sun exposure 15 times longer than it can in an unprotected state. Skin care experts worry that such calculations will encourage people to remain exposed to the sun for long stretches of time without reapplying sunscreen.
Why choose SPF 40 or 50? It's a max-protection option for fair-skinned people, winter activities and adventurers spending prolonged time at high elevations.
Note: Though some products (including a few offered at REI) carry SPF ratings of higher than 50, "50+" will likely be the highest rating claim permitted by the FDA on future sunscreens. Terms such as "sunblock" (no sunscreen truly blocks all UV light) and "all-day protection" (reapplication is advised after 2 hours of exposure) will also likely vanish from use.
Q: If a sunscreen's SPF number applies only to UVB rays, why does no rating system exist for UVA rays?
A. The FDA began studying a UVA rating system in 2007 and work is ongoing. Because use of the term "sunscreen" in labeling subjects the ingredients to be regulated as drugs, sunscreens fall under the FDA's oversight. The FDA so far has recognized 17 sunscreen ingredients as "Generally Recognized As Safe and Effective" (GRASE). To repeat what was noted earlier in this article, the following ingredients are cited by the FDA for offering broad-spectrum (UVA and UVB) protection:
- Benzophenones (often identified as oxybenzone)
- Cinnamates (often identified as octinoxate or cinoxate)
- Ecamsule (often marketed as Mexoryl or Mexoryl SX)
- Sulisobenzone
- Salicylates
- Zinc oxide
- Titanium dioxide
- Avobenzone (sometimes marketed under the name Parsol 1789; better when stabilized with oxybenzone or Helioplex)
Not on the list but also believed to be a good UVA inhibitor: menthyl anthranilate. Outside the U.S. other ingredients are being used in sunscreen are believed to be very effective against UVA. Some have dizzying names such as diethylamino hydroxybenzoyl hexyl benzoate. The medical press has reported that some of these ingredients are under review by the FDA for eventual use in the U.S.
How Sunscreen Works
Q: How does sunscreen shield my skin from UV light?
A. Sunscreens absorb, reflect or scatter UV rays. Active ingredients in so-called "chemical" sunscreens (salicylates, cinnamates, oxybenzone, octylcrylene, et al.) absorb UV light and prevent it from impacting your skin. Titanium dioxide and zinc oxide (the compounds that years ago created the white-nose effect on lifeguards), physically reflect or scatter sunlight, directing it away from your skin. The original formulas of these "physical" sunscreens remained white when applied to the skin; happily, newer formulations blend in with skin tones.
Q: Can sunscreen really be "waterproof"?
A. "Water resistant" is a more accurate description. All sunscreens lose some degree of effectiveness when skin is submerged in water. Sunscreens labeled as "waterproof," "sweatproof" or "extreme" include ingredients designed to help lotions or creams better adhere to skin. But even these sunscreens will have their effectiveness diminished following prolonged contact with water or profuse, extended sweating. In such situations, it is wise to reapply sunscreen regularly—approximately every 90 minutes or less (check label instructions). It is believed spray-on sunscreens are more vulnerable to being washed off skin more quickly that lotions or creams.
Q: What is PABA?
A. Para-aminobenzoic acid (PABA) is an ingredient once commonly found in sunscreens, though it is rarely used today. PABA was found to cause allergic and photosensitivity reactions and it had the potential to stain clothing. Many product labels promote the fact that their sunscreen is "PABA-free."
Tips for Using Sunscreen
Q: How much sunscreen should a person apply?
A. Skin-care professionals typically recommend one ounce for full-body coverage, an amount that would fit a shot glass. The American Academy of Dermatology recommends that people should "generously apply sunscreen to all exposed skin." Be especially vigilant in treating thin-skin areas such as noses, ears and, for sandal-wearers, the tops of feet. Applying sunscreen too thinly could minimize its ability to absorb or reflect UV light.
Q: When should sunscreen be applied?
A. On dry skin between 20 and 30 minutes before sun exposure begins, enough time for your skin to absorb it.
Q: When should it be reapplied?
A. Some skin care experts say as often as every 2 hours. Consider reapplying after periods of profuse sweating or regular contact/abrasion with vegetation or rock surfaces. Applying sunscreen to sweaty skin is less than ideal. When it's time to reapply, try to find a shady spot to take a snack break, giving your skin time to cool and dry a little. If possible, it's best to reapply sunscreen 20 to 30 minutes before you resume activity.
Be aware that the color of your skin during an outdoor activity is usually a poor guide to what impact the sun is having on your skin. Evidence of sunburn may not appear for up to 24 hours.
Q: When do I really need to use it?
A. Any day that includes extended time outdoors, skin-care experts say, even cloudy days, since UV light (particularly UVA) can penetrate clouds. UVA also passes through most glass. It is most important between the hours of 10am and 4pm, when sun intensity peaks. A good rule of thumb: The sun is most intense whenever your shadow is shorter than you.
Natural elements can also work against you. Sand, snow, ice and water can all reflect up to 80% of UV rays, intensifying the overhead exposure you are already experiencing.
Q: What other factors might influence my use of sunscreen?
A. Skin type: Fair-skinned Caucasians (especially people with freckles and blond or red-haired individuals) need to be particularly diligent in applying sunscreen (or shielding their skin with clothing and hats). The following chart reflects both past and present FDA guidance for evaluating skin types:
| Type | Sun History | Example |
| I | Always burns, never tans; extremely sun-sensitive skin | Pale white; red-headed, freckled, Irish/Scots/Welsh |
| II | Burns easily, tans minimally; very sun-sensitive skin | White to beige; fair-skinned, fair-haired, blue or green-eyed, Caucasian |
| III | Burns moderately, tans gradually to light brown; minimally sun-sensitive | Beige; average skin |
| IV | Burns minimally, tans well to moderate brown; minimally sun-sensitive | Light brown; Mediterranean-type Caucasians |
| V | Rarely burns, tans profusely to dark brown | Moderate brown; Middle Eastern, some Hispanics, some African-Americans |
| VI | Never burns, tans profusely | Dark brown or black; African-American |
Altitude: The higher you ascend, the thinner the atmosphere (and the UV-inhibiting gases contained in it). It is estimated that UV radiation increases 4% per 1,000 feet of elevation gain. Therefore, at higher elevations, you should more conscientiously apply and reapply sunscreen.
Latitude: Sun intensity becomes greater the closer you are to the equator, upping your need for diligent use of sunscreen and other sun-protection strategies.
Temperature, humidity: High levels of either will trigger increased perspiration, diminishing your sunscreens potential for effectiveness.
Abrasion: Bushwhacking or scrambling typically means your skin will be brushing against other surfaces. Toweling off after a swim will no doubt remove some or all of your protection. Reapply as needed.
Exertion: Heavy perspiration usually mandates one of more reapplications during a day-long activity.
Q: What if I have specific concerns about my particular skin type?
A. Consult your personal physician or a dermatologist.
Q: Does it matter in what form sunscreen is applied?
A. Lotions and creams are the most common delivery systems for sunscreen. Sprays are sometimes preferred by parents (kids often accept sprays more willingly) and people with above-average body hair.
Kids, Longevity and More
Q: Can children use sunscreen?
A. Skin care experts say children older than 6 months should use sunscreen. Infants under 6 months, whose skin might too easily absorb the chemicals used in sunscreen, should be physically shaded from the sun.
Adult sunscreens are fine for use on children older than 6 months. Some sunscreens marketed as kid-specific simply add fragrances believed to be appealing to children but are otherwise no different than adult formulas.
Q: Does sunscreen lose its effectiveness over time?
A. Theoretically, active ingredients can degrade as time passes. Look for an expiration date on the container. If none is shown, a general rule is to replace sunscreen 4 years after purchase.
REI is sensitive to consumer skepticism that such a guideline is rooted in the desire to simply sell more sunscreen. While an older sunscreen may still be effective in protecting skin from sunburn-causing UVB light, the aging effects of UVA rays will not be so readily apparent. Thus we offer the general guideline (replace after 4 years) while encouraging customers to use their best judgment.
Q: Can I use sunscreen and insect repellent at the same time?
A. Yes, but the effectiveness of both will be diminished. Even so, here's a suggested strategy: Apply sunscreen on dry skin 20 to 30 minutes before your activity starts. After that time has passed, apply the repellent. You'll likely need to reapply both at some points during an all-day activity. The same advice stands: sunscreen first, repellent second. Also, a few sunscreen/repellent combos are available.
Q: Why is a particular type of sunscreen effective on me but not on a friend?
A. Body types, activity levels, where and when the sunscreen is used — many variables can affect sunscreen performance. Sample a number of brands to see if one works particularly well for you.
Also, try to avoid exposing sunscreen to high heat (such as leaving it in the trunk of a hot vehicle).
Men, surveys have shown males are less inclined to use sunscreen than females. Our advice: Get with the program. Avoiding sunburned earlobes and wrinkled skin before you're 50 are just a couple of the many payoffs for using sunscreen.
Q: Who makes the sunscreen that carries the REI label?
A. Florida-based Sawyer Products, which also manufactures many products for military applications.
Q: What differentiates the choices in this product line?
A. Multilevel Protection SPF 30: Designed for all-around, general-purpose use; designed to feel light on skin and not clog pores.
Extreme Protection SPF 50: Includes titanium dioxide for an elevated level of UVA protection. Because it is designed to adhere well to warm, moist skin, Sawyer considers this formula a good choice for the reapplication of sunscreen on already-sweating skin during activity. Feels greasier and warmer than its other formulas, but it excels at bonding with skin. Good for glacier or equatorial travel.
