July 15, 2016
6 min read

Sunscreen decoded: Myths about SPF, labels, recommendations

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Edward A. Bell

The most important aspects of sunscreen use in the summer months (and all year long) can likely be summarized in just a few words: Apply a lot of sunscreen liberally to the body, and apply it repeatedly and often when exposed to the sun’s rays. Unfortunately, many do not heed this advice and may be at increased risk for skin cancer years later.

Are sunscreen products with higher SPF (sun protection factor) values better to use? How much sunscreen should be applied? Are there differences in the numerous sunscreen products? Do pediatricians routinely recommend sunscreen use to their patients? These questions will be addressed in this month’s column.

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Excessive, unprotected time spent exposed to the sun’s radiation is a well-known modifiable risk factor for the development of skin cancers, including melanoma, squamous cell carcinoma and basal cell cancer. Sunlight as ultraviolet A (UVA) and B (UVB) radiation can result in sunburn, premature skin aging and skin cancer. While damaging effects from UVB occur mostly in the summer months as sunburn, damage resulting in skin aging and skin cancer can occur throughout the year from UVA, as well as UVB. Skin cancer is one of the most common forms of cancer in the United States, with one in five individuals developing skin cancer in their lifetime.

Sunscreen characteristics and misconceptions

Both the AAP and the American Academy of Dermatology recommend use of sunscreen with an SPF rating of at least 15 or 30 to minimize risk for skin cancer and aging. While SPF may be familiar to the public, the true meaning of an SPF rating is easily misunderstood. A product’s SPF relates to the amount of UV radiation (primarily as UVB) that is necessary to produce minimal skin erythema, or sunburn, without sunscreen, relative to the amount of UV radiation required to produce similar skin erythema with sunscreen use.

However, SPF is not a direct measure of how long one can spend in the sun before developing a sunburn, as is commonly believed. SPF is primarily an indication of UVB protection, as UVB radiation is more erythemogenic than UVA radiation. Equally misunderstood is the nonlinear UVB protection of SPF rating: an SPF of 15 blocks 93% of UVB radiation, while an SPF of 30 blocks 97%, and an SPF 50 blocks 98% of UVB radiation. One may easily believe that an SPF 30 sunscreen is “twice as good” as an SPF 15 sunscreen, potentially resulting in more time spent in sunlight, and adversely, increased risk for damaging UV radiation.

A recently published evaluation by Kong and colleagues of consumer knowledge on sunscreens confirmed these concerns: Consumers displayed an overreliance on SPF rating, low knowledge of an adequate amount of sunscreen to apply, as well as product characteristics that protect against skin cancer and skin aging. As UVA radiation can result in skin aging, use of a sunscreen product with protection from UVB and UVA, or “broad spectrum,” is best used and is recommended.

In 2012, the FDA established improved regulations for sunscreen product labeling. These new regulations include labeling that a product stated as “broad spectrum” and SPF 15 or greater will help protect from sunburn, skin aging and skin cancer. Sunscreen products that are not broad spectrum (no UVA protection) with an SPF less than 15 can only be labeled to provide protection from sunburn, and not skin aging or skin cancer. Sunscreens can no longer claim to be waterproof, but can be labeled as “water-resistant” for 40 or 80 minutes only (time for SPF protection while swimming or sweating). In addition, no sunscreen can be labeled with an SPF greater than 50 and now will be labeled as SPF 50+ as a maximum rating.


Sunscreen application errors

Common mistakes made by sunscreen users include application of an inadequate amount and too few reapplications. An adequate amount of sunscreen to apply to all exposed areas generally is described as about 2 ounces, or 4 tablespoonsful. As 4 tablespoons is equivalent to 12 teaspoons, this amount can be distributed as such: 2 to 3 teaspoons to the face/neck/head, 1 teaspoon to each arm, 2 to 3 teaspoons to each leg/foot, and 4 teaspoons to the chest and back. Other amount analogies include total body application of a shot glass full, or a total amount of sunscreen that will fill a child’s cupped hand. This amount should be applied every 2 hours when in the sun and even more often when swimming.

As one can imagine, a large bottle of sunscreen should not last long for a family, especially during the summer months. Otherwise, it is likely that not enough sunscreen is being applied. Several published studies have demonstrated that an inadequate amount of sunscreen applied (an adequate amount is described as 2 mg/cm2) results in a clinical reduction in SPF protection (eg, an inadequate application of an SPF 30 sunscreen can result in actual SPF 8 protection). These studies have demonstrated that users may commonly apply 25% to 50% of the recommended amount. Sunscreens are best applied 15 to 30 minutes before sun exposure, to allow the active ingredients to dissolve into skin layers.

Sunscreen choices

A trip to the local pharmacy will find many sunscreen products for sale. How do they differ? Which is best? Products labeled as broad spectrum with an SPF of at least 15 or 30 should be used. Sunscreens are available in a variety of dosage forms, including liquid creams, sprays, gels and sticks, with some advertised for children. Any of these forms are likely to be effective, if used properly. Sprays, while perhaps easy and convenient to apply, may suffer from too little being applied (ie, one spray may not be enough). Sprays are best used by spraying the product into one’s hands in an adequate amount, and then applying. Gels may be good for the scalp or male chest.

Consumer Reports frequently rates sunscreen products, and their latest evaluations are published in the July 2016 issue. In this evaluation, 65 products with an SPF of 30 or higher were tested for SPF protection on skin, and 43% of the tested products did not provide the labeled SPF protection. Several products recommended by Consumer Reports include: No-Ad Sport SPF 50 Lotion, Pure Sun Defense SPF 50 Lotion (unscented), Banana Boat SunComfort Continuous Spray 50+ (coconut scent), or Coppertone Water Babies SPF 50. Other products are listed in this Consumer Reports issue.

Sunscreen use in pediatrics and pediatricians’ recommendations

Some published evidence indicates that children and adolescent sun protection behavior is less than desired. Data evaluated from the Youth Risk Behavior Surveillance System during a 10-year period (2001-2011) demonstrated that high school-aged children reported a declining use of sunscreen (67.7% in 2001 vs. 56.1% in 2011).

Nearly 30% of white females reported using a tanning bed in 2011, according to Basch and colleagues. In a study of periadolescent children, 360 participants were surveyed about sun behaviors at ages 10 and 11 years, and again 3 years later. More than 50% of these children reported at least one sunburn during the previous summer on both surveys, while sunscreen use declined from 50% to 25% during the follow-up survey, Dusza and colleagues wrote. Information gathered from these studies is important in light of epidemiologic data indicating that a history of five episodes of sunburn per decade increases the risk for melanoma by threefold.


Data on sun protection counseling given by physicians is equivocal. Some surveys suggest that pediatricians commonly counsel their patients on sun protection and sunscreen use. In a recently published study by Akamine and colleagues, information from the National Ambulatory Medical Care Survey was analyzed to identify patient visits to outpatient physician offices (1989-2010) during which sunscreen was recommended. Overall, mention of sunscreen use was reported by physicians at 0.07% of visits. Dermatologists recorded the mention of sunscreen the most (86.4% of visits). By 10-year age category, sunscreen was recommended the least for children aged younger than 10 years, and children/adolescents were recommended sunscreen the least compared with all patient age groups. Pediatricians recommended sunscreen at a low number of visits (0.01%).

Disclosure: Bell reports no relevant financial disclosures.