by Henry W. Lim, MD
In a few short decades, sun protection has come a long way. Suntan lotion has been replaced by sunscreen; metal reflectors have given way to shade umbrellas. Simple veils or visors to shield the eyes have been superseded by wide-framed UV-blocking sunglasses.
Nowhere is this evolution more evident than in the ever-improving quality and effectiveness of sunscreens.
In the Beginning
In 1918, Norman Paul of Sydney, Australia, first made the link between sun exposure and skin cancer in print with his book, The Influence of Sunlight in the Production of Cancer of the Skin. Paul also anticipated the current trend for sun-protective clothing when he recommended covering the skin with veils.
But fabric wasn't the only form of sun defense around: "Zinc cream," containing zinc oxide paste, was also a popular sunburn preventative. Zinc oxide is what's known as a physical, inorganic sunscreen: A mineral substance that reflects the sun's rays away from the skin, it has always been one of the most complete sunscreens. However, back then, it came in a thick, opaque paste that left a noticeable white cast on the skin. Because of its texture and paint-like appearance, it was not popular. It was mainly used on the nose, a prime spot for sunburn.
As sunscreens evolved, a key focus in their improvement was expanding their protection across the UVB and UVA ranges. There are two components of the sun's ultraviolet radiation (UVR) that reach the surface of the earth: long-wavelength, ultraviolet A (UVA), and short-wavelength, ultraviolet B (UVB) rays. UVA is divided into two categories: UVA1, measuring from 340-400 nanometers (billionths of a meter) and UVA2, ranging from 320-340 nanometers. UVB rays are 290-320 nanometers. Different sunscreens either reflect or absorb various portions of the UV spectrum; the more portions they cover, the better.
It was once thought that only UVB radiation, the main cause of sunburn, significantly damaged the skin and raised one's risk of skin cancer; for many years, UVA was not considered dangerous. Sunscreens were thus constituted accordingly - protecting mainly against UVB. But research in the past 20 years has shown that cumulative UVA exposure was the key cause of skin aging and wrinkling (photoaging), and also played a contributory role in the development of skin cancer. As these new research findings have occurred, it has become clear that there is a significant need to improve the UVA protection of sunscreens.
Enter Technology, and Commerce
Chemical sunscreens, now known as organic sunscreens, unlike physical (also know as inorganic) ones such as titanium dioxide and zinc oxide, absorb rather than reflect UVR and are made of organic materials. As early as 1911, researchers had been investigating chemical combinations for sun protection. This led in 1928 to introduction of a sunscreen blending the UVB absorbers benzyl salicylate and cinnamate. And as new sunscreens developed, so did the market: In 1936, L'Oreal founder Eugene Shueller introduced Ambre Solaire, made with benzyl salicylate. This was the first commercially available sunscreen product. Part of the appeal of these products was that they were not conspicuously visible like the otherwise effective zinc oxide paste which was available at that time.
Sunscreen gained new importance during World War II. At the request of the Army Air Force Material Center, in 1942 researchers from General Electric Lighting Laboratories and the Western Reserve Medical School tested substances that could help prevent sunburn among soldiers exposed to the tropical sun in the Pacific. The investigators determined that the best delivery vehicle would be stable, non-toxic, inexpensive and "reasonably waterproof." Red Vet Pet (for Red Veterinary Petroleum), a sticky red petroleum developed by future Coppertone founder Benjamin Green, fulfilled these requirements; researchers recommended adding 10 percent phenyl salicylate, a UVB absorber, to it. This active ingredient had been used in two Australian sunscreens and is estimated to have had an SPF of about 4.
In 1943, the UVB absorber PABA (p-aminobenzoic acid) was patented. Dermatologists prescribed 2-5 percent PABA in an alcohol base, but it caused allergies in some users and raised some fears of a link to cancer development; in addition, it causes yellow staining on clothing. Therefore, although PABA is still FDA-approved for use in sunscreen, by the mid-1980s, its popularity had declined sharply.
The Dark Ages
From the mid-20th century on, tanned skin reigned supreme. Between a media that glorified the "healthy tan," the advent of the bikini and the popularity of outdoor sports, tans were synonymous with health and beauty. A sunburn was often considered a necessary evil in the quest for a tan.
In 1972, the FDA reclassified sunscreens from cosmetics to over-the-counter drugs, and labeling requirements became stricter. However, consumers continued to soak up the sun with so-called "suntan lotions" - low-SPF products that provided only minimal defense against the sun's UVR, reducing sunburn and allowing users to stay out longer, therefore "promoting suntanning" and "giving a deeper, darker suntan."
New Products, New Attitudes
In 1956, Rudolf Schulze modified a little-used sun protection measurement system first introduced in 1934. But the Schulze system languished until 1974, when Swiss chemist Franz Greiter adapted Schulze's formula and dubbed it SPF, or Sun Protection Factor. SPF is a representation of the defense against UVR's burning radiation, which is predominantly UVB. SPF number is the ratio of how long it will take for the sun to redden the skin when using sunscreen, compared to how long the skin would take to redden without it. For example, someone properly using an SPF 15 sunscreen should be able to go 15 times longer without burning than someone not using sunscreen.
Innovations continued throughout the decade: Johnson & Johnson introduced the water-resistant Sundown Sunscreen, and Coppertone started labeling its products with SPF numbers; its Super Shade SPF 15 Lotion - the first U.S. sunscreen with an SPF 15 - debuted in 1978. (The Skin Cancer Foundation considers SPF 15 the minimal SPF for acceptable sun protection.) But even as sunscreens became more sophisticated, tanning's popularity continued to grow with the introduction of indoor tanning booths to the U.S. in the late 1970s. (In fact, tanning booth operators often promoted their service by erroneously claiming that tanning booths are a safer way to tan than sun exposure.)
However, the harmful effects of cumulative sun exposure were becoming increasingly obvious. Skin cancer rates were climbing, and the FDA made the connection in print in a 1978 monograph, noting: "Overexposure to the sun may lead to premature aging of the skin and skin cancer." The publication also introduced labeling guidelines for sunscreens and adopted the SPF measurement system. In 1981, the Skin Cancer Foundation introduced its Seal of Recommendation program that assesses the safety and efficacy of sunscreen products.
The UVA Problem
In the 1980s the term "suntan lotion" began to disappear as consumers learned more about the importance of sun protection. But while many sunscreens shielded effectively against UVB rays, it was becoming clear that greater protection was also needed against UVA.
In the 1980s, the only commonly used UVA-protective sunscreens were the physical blockers titanium dioxide and zinc oxide. These sunscreens were unappealing to users, and manufacturers sought new ingredients. In 1980 Coppertone introduced For Faces Only: This contained oxybenzone, the first chemical filtering ingredient that offered limited but significant protection against UVA rays. Subsequently three other ingredients were introduced that protected against limited degrees of the UVA spectrum: dioxybenzone, meradimate, and sulisobenzone. The term "broad spectrum protection" started being advertised on sunscreens that contained any of these.
But the need for a sunscreen that protected against the full UVA spectrum remained. Avobenzone, a chemical approved by the FDA in 1988, was considered the next quantum leap forward, protecting against a much broader range of the UVA spectrum. But eventually concerns arose about avobenzone's photostability - its ability to maintain its screening power following sun exposure; UV was found to break it down rapidly. Thus, in just the past two years chemists have started incorporating stabilizing ingredients such as octocrylene into sunscreen formulas. Technologies such as HelioplexTM, Active Photobarrier ComplexTM, AvoTriplexTM, SunSureTM, DermaplexTM, etc, now provide photostabilized avobenzone.
Kid-Friendly Sun Safety
In the '90s, new techniques and formulas resulted in products that were not only easy to use but appealing to kids. No-rub sunscreen gels, sprays and sticks as well as colored, scented and glittery formulas made sun protection fun.
Sunscreen's Present and Future
In 2006, the FDA approved a long-awaited new organic UVA filter, ecamsule (a.k.a. Mexoryl SXTM) that is not degraded by sun exposure (i.e., is phototable) and blocks a significant portion of the UVA spectrum. Meanwhile, chemists have continued to improve sunscreens' look and feel: Most important, "micronized" versions of zinc oxide and titanium dioxide (with smaller particle size) have eliminated the thick, streaky look associated with these excellent UVA-UVB-blocking ingredients, allowing people to apply them all over the body without any whitish appearance due to the product. In addition, improved delivery systems like liposomes (sac-shaped nanoparticles) have helped ensure that sunscreen stays on the skin's surface longer.
In August, 2007, the FDA proposed new regulations for sunscreen labeling for the first time since 1999. These proposals may take two years or more to implement, but should help consumers better understand just how much protection a sunscreen can provide. Although there is some discussion about the details, in general this proposal has been well-received by The Skin Cancer Foundation as well as by all professional organizations in dermatology. [For more on the FDA's proposals, see "Sunscreen: Truth in Labeling," on p. 77.]
1918 - Influence of Sunlight in the Production of Cancer of the Skin published.
1920s - After falling asleep on a nobleman's yacht off the coast of France, a bronzed Coco Chanel helps to popularize the tan.
1928 - The first chemical sunscreen- a combination of benzyl salicylate and benzyl cinnamate - is created.
1934 - Ultraviolet protection quotient system introduced by Ellinger.
1936 - L'Oreal founder E. Schueller introduces Ambre Solaire, the first commercially available sunscreen.
1943 - PABA patented.
1946 - Jacques Helm and Louis Reard introduce the bikini, thrilling sun worshippers everywhere.
1948 - GE advertises its Sunlamp for home use: "Get that golden, glowing summer-tan look! GE Sunlamp tans like the sun!"
1953 - Little Miss Coppertone debuts.
1960 - Coppertone introduces QT (for Quick Tan), a sunless tanner with dihydroxyacetone (DHA).
1962 - Rudolph Schulze uses the reciprocal of Ellinger's quotient to determine sun protection level, which shows how long it will take for your skin to burn with protection compared to without.
1972 - Sunscreens are reclassified as over-the-counter drugs rather than cosmetics.
1974 - Franz Greiter uses the term SPF for "Sun Protection Factor" to describe the outcome of Schulze's testing methods.
1978 - The FDA introduces SPF numbering system to U.S.
- Tanning booths start to appear in the U.S.
1980 - Coppertone's For Faces Only, providing protection against UVA rays, hits the U.S. markets.
1981 - The Skin Cancer Foundation introduces the Seal of Recommendation.
1988 - Chemical UVA absorber avobenzone approved by the FDA.
2006 - The FDA approves ecamsule (a.k.a. Mexoryl SXTM).
2007 - The FDA proposes new rules for measuring and labeling UVA protection.
Dr. Lim is the Chairman and Clarence S. Livingood Chair of the Department of Dermatology at Henry Ford Hospital in Detroit; he is also Vice President for Academic Affairs. He is the Vice President of the American Academy of Dermatology and has been an officer and on the board of several dermatological societies. He is the Associate Editor of the Journal of Investigative Dermatology and is on the editorial board of the American Academy of Dermatology. He has authored hundreds of articles and several textbooks. He is a long-time member of The Skin Cancer Foundation's Photobiology Committee.
 Groves, GA. The sunscreen industry in Australia: past, present and future. In Sunscreens: Development, Evaluation, and Regulatory Aspects. 2nd edition. Lowe NJ, Shaath NA, Pathak, MA (eds). Marcel Dekker, New York, 1997, 229.
 Osgood, PJ, Moss, SH, Davies, DJ. The sensitization of near-ultraviolet radiation killing of mammalian cells by the sunscreen agent para-aminobenzoic acid, Journal of Investigative Dermatology, 1982, 79, 6.
 Berube, D. Nanomaterials and risk: appropriate use of the technical data. Delivered on Oct. 10, 2006
at the Public Meeting on Nanotechnology Materials in FDA Regulated Products at the Natcher Auditorium, Bethesda, MD. http://www.fda.gov/nanotechnology/meetings/berube.html.
 Armstrong, L. Don't burn, baby, don't burn: new sunscreens, monitors, and high-SPF clothes can help ward off harmful rays. BusinessWeek, July 3, 2006. http://www.businessweek.com/magazine/content/06_27/b3991090.htm