Also, unlike previous generations, today there are over 400 medications prescribed that leave patients with an increased sensitivity to sun exposure and a heightened susceptibility to sun damage. The lengthening of the average life expectancy is an additional contributing factor.
(excerpted from Therapeutic SunCare)
Greater awareness, increased patient concern, and improvements in diagnostic techniques may help to decrease this alarming rise in the rate of skin cancer. Perhaps the most important factor in the rise of skin cancer rates is the increase in exposure to the UVA wavelength. Previously thought of as harmless, the UVA wavelength is now known to contribute significantly to skin damage, skin cancer, DNA damage, and immune system suppression. UVA rays penetrate the skin deeper and, unlike UVB rays (which cause initial redness and burning), create damage that is not immediately detected.
Because UVA rays remain constant throughout the year and during the entire day, people are exposed to them continually, whether it is midday in July, or 4 p.m. on an overcast winter afternoon. When it comes to the appearance of the skin, wrinkling and thinning of the skin are often thought of as a natural aging process. We now know that these effects are primarily the result of long-term exposure to sunlight. Cumulative exposure to the sun damages the epidermis (the outer layer) and the dermis, (the deeper layer where the skin’s framework exists), causing elastin fibers to thicken and become more numerous. Damage to the collagen causes it to undergo degradation. As a result of this degradation, “reticulin” fibers are deposited throughout the entire dermis, rather than remaining in the limited region outlining the specific dermal-epidermal junction.
With some simple and consistent steps, sun damaged skin can be avoided, even repaired. Sun related damage can be minimized and some damage can be reversed. A crucial step, however, is one’s awareness that sun protection must be used daily and year-round. Children, in particular, need to use sunscreen. Frequent sun exposure and sunburn in childhood must be avoided as these appear to set the stage for high rates of melanoma in later life. A comprehensive sun protection program includes the use of sunscreen as well as the use of sun-protective clothing, sunglasses, and sun avoidance between 10 a.m. and 4 p.m.
The Facts of Light:
• Every seven minutes someone dies of Melanoma.
• Sun damage to the skin is cumulative.
• Not all skin is the same. Different skin types respond differently to sunlight. Know your skin type and determine what exposure is safe for you.
• A suntan can do you more harm than good. A suntan is actually a sign of skin damage. Any level of tanning indicates photo-damage that will lead to wrinkling, aging, and skin cancer.
• The skin has a memory of all the sun damage that has happened to it over the entire life of an individual. A high cumulative effect results in a greater susceptibility to skin cancer.
• Normal, healthy skin acts as a barrier and protects us from injury. Our skin regulates our temperature, receives sensory impulses, and synthesizes vitamin D.
• The skin is the largest organ in the human body.
• More than 90 percent of non-melanoma skin cancers occur in fair skinned people who tend to burn. However, even though the incidence of skin cancer is lower in dark skinned people, they are still susceptible to the damaging effects of UV radiation. They are also susceptible to the effects of the sun on the eye and on the immune system.
Sunlight has its Benefits…
Sunlight is a primary source for vitamin D. This helps keep our bones strong. The current recommended daily intake of vitamin D is 200 IU from birth to age 50, 400 IU between age 51 and 70, and 600 IU after age 71. Recent studies suggest that 1,000 IU a day may reduce the incidence of certain cancers — such as cancers of the ovary, breast, and colon — by as much as 50 percent. That is because vitamin D strengthens the immune system and supports cell growth. Vitamin D requirements can be fulfilled: through dietary sources (a serving of oily fish contains between 250 and 360 IU, and one tablespoon of cod liver oil has 1,360 IU); or through supplements (alone or combined with calcium).
Why SPF is Not Sufficient
A number assigned to a sunscreen represents the factor by which the time required for unprotected skin to become sunburned can be increased through the application of a sunscreen. Also called sun protection factor (SPF).
It is important to recognize that an SPF rating does not adequately measure protection from all the damaging radiation effects of light. SPF is only a determination of protection from one specific wavelength of ultraviolet radiation, the UVB wavelength (290nm–320nm). Unfortunately, there is no currently approved or accepted standard in the United States to rate the quality of a sunscreen’s protective capabilities concerning UVA wavelengths. UVA (320nm–400nm) is the deeper penetrating wavelength, more often associated with the signs of photo-damage, such as wrinkling, pigmentation changes, and dryness. The SPF rating system does not accurately or completely define a sunscreen’s protective capabilities from all harmful ultraviolet radiation, ONLY the UVB wavelength.
UVB exposure results in a red, painful irritation first experienced during early sun exposure, but UVB is not the only ultraviolet wavelength damaging to the skin. In fact, UVB causes only a minimal effect upon the deeper depth of skin. However, UVA damage penetrates much deeper. Therefore, UVB and UVA radiation are both recognized as causes of skin cancer. SPF 30 is not enough to address the full effect of ultraviolet light on the skin, only UVB.
The technical explanation of the benefits of 30+ SPF is complicated. For instance, an SPF 15 product blocks 93 percent of incidental UVB light, while SPF 34 blocks 97 percent of incidental UVB, a seemingly insignificant difference. However, Dr. Kays Kaidbey completed an instructive model using human skin volunteers. He showed that when skin was exposed to enough simulated solar radiation to cause the beginning of redness, skin protected with an SPF 30 sunscreen suffered 2.5 times fewer sunburn damaged cells than skin protected with an SPF 15 sunscreen. Thus came the knowledge that there is at least a two-fold difference in the protection offered by higher SPFs.
The Facts of Light
• Use of a higher SPF sunscreen helps overcome “user-errors”: e.g., in general, sunscreen use is sporadic, and reapplication is not frequent enough or with enough sunscreen.
• The accuracy of the SPF number is questionable. A greater amount of sunscreen is generally applied during testing than when sunscreen is applied during general use. This creates the reality that the true SPF number is about 1/2 or 1/3 of the stated number
• When utilizing titanium dioxide and zinc oxide, the higher the SPF, the greater the UVA coverage.
• SPF merely addresses the UVB wavelength not the UVA, UVC, visible, or infrared light wavelengths.
• The UVA ray is more difficult to study on human subjects due to the length of time it takes for UVA skin damage to appear. Aging of skin or the mutating of skin cells is a cumulative effect and can take decades to manifest fully.
Sun Protection Factor Efficacy
SPF Value ---- %UV Rays Absorbed or Reflected ---- %UV Rays Transmitted (1/SPF Value)
2 ---- 50% ---- 50%
4 ---- 75% ---- 25%
6 ---- 83.33% ---- 16.7%
8 ---- 87.5% ---- 12.5%
10 ---- 90% ---- 10%
15 ---- 93.33% ---- 6.7%
25 ---- 96% ---- 4%
30 ---- 96.78% ---- 3.3%
35 ---- 97.14% ---- 2.8%
40 ---- 97.5% ---- 2.5%
50 ---- 98% ---- 2%
60 ---- 98.4% ---- 1.6%
100 ---- 99% ---- 1%
The Chemistry of Sunscreen
Myths concerning sunscreens abound, such as the following:
Myth: Applying sunscreen every morning affords ample sun protection.
Truth: Frequent and adequate reapplication of a full spectrum sunscreen is essential due to moisture loss and rubbing.
Sunscreen: (s n skr n ) n. Chemical or physical agents that protect the skin from sunburn and erythema by absorbing or blocking ultraviolet radiation. A preparation, often in the form of a cream or lotion, used to protect the skin from the ultraviolet rays of the sun.
Sunscreens use chemical absorbers and/or physical blockers formulated to protect the skin. This section provides brief technical descriptions of how sunscreens work.
PHYSICAL BLOCKERS: As physical blockers, sunscreens fall into three categories:
• Direct physical blockers
• Indirect blockers that assist by increasing distribution of direct blockers
• Polymers, often starch derived, that substantially increase the effective length of the pathway that the sun’s rays must travel to reach the skin.
Direct Physical Photoblockers
Most of the physical photoblockers are compounds of naturally occurring metals (iron, chromium, zinc, titanium, etc). While some, such as bismuth, are man-made. In addition to their photoprotective attributes, these substances also assist in preventing windburns and the skin damage that results from wind driven micro particles of dirt and grime. An additional significant property of these physical blockers is their ability to offer a defense against infrared (“heat”) rays. They do so by two distinct means.
First, particles large enough to be visible (i.e. to reflect visible light) also reflect and refract the infrared waves most harmful to skin (760nm—1,800nm). Second, regardless of their particle size, these metal-based materials act as a “heat sink” and thereby reduce the heat effect on the skin.
Three important photoprotective blockers are discussed in this section: Titanium Dioxide Zinc Oxide, and Iron Oxides.
Titanium Dioxide is widely used as a white pigment powder in cosmetics. The purpose of incorporating large particles of titanium is to give opacity to the products containing it, and to lighten (or whiten) their color. Opaque titanium dioxide greatly reflects and scatters all UV and visible rays. It also reflects much of the skin-damaging waves of infrared light. This keeps the skin cooler, reduces “heat” damage, and prevents subsequent photoaging.
To photo-stabilize titanium dioxide, it must be micro-coated with protectants such as silicone or aluminum oxide. Since titanium dioxide spreads poorly on the skin, an additional process must be incorporated to ensure that its protective effect is spread evenly over the skin surface. To achieve cosmetic elegance and usefulness, micro-coating of the titanium dioxide is employed. This is facilitated by designing a vehicle that assures good, even application to the skin. This step is essential. Large particle titanium dioxide products produce a very white, opaque appearance on the skin when applied. Therefore, submicronizing the titanium dioxide powder is performed. The process of submicronization creates small particles that effectively create a larger surface area, better able to absorb visible light. This enables the resultant product to offer highly efficient sun protection that helps protect the skin from a great deal of both UVB and UVA radiation, while remaining invisible on the skin.
Transparent (sub-micronized) titanium dioxide works by absorbing, reflecting and scattering most UVB and some UVA rays. Additionally, protection against UV, visible and infrared is significantly limited when submicronized titanium dioxide is the primary protectant.
Zinc Oxide has been known and used topically for centuries as a skin protectant and wound healing adjuvant. It has been recognized as a mild antimicrobial agent. More than 50 years ago, zinc oxide was used as a block for ultraviolet light (UVB/UVA). It also reflects infrared light from the skin, as does titanium dioxide. Its ability to protect in the long UVA range, (300—400 nm), however, is much higher than that of titanium dioxide. Zinc oxide absorbs, rather than scatters most UVA, while titanium dioxide primarily scatters these wavelengths. Thus, formulated in combination with titanium dioxide, ultrafine zinc oxide “closes the window” in the UVA range. Zinc oxide works to both complement titanium dioxide’s protection and to extend photoprotection to the skin where titanium dioxide is insufficient. The optimal particle size range for ultraviolet blocking zinc oxide (without blocking visible wavelengths) is approximately 80 to 150 nanometers. (1,000 nanometers = 1 micron)
We most commonly see iron oxide in two areas; as rust on exposed iron and in cosmetics, where it is employed to give the cover-up color desired. While not approved by the FDA as an active ingredient in sunscreens, many companies use iron oxides in their sunscreen products. Cosmetic iron oxides are man-made to very high levels of purity, desired color and particle size.
Iron oxide pigments for cosmetic use are micronized powders. By controlling the purity, particle size, temperature, and rate of drying during manufacture, they have become available in a number of shades and tones of red, yellow, black, and brown (and blends of these basic colors). These cosmetic pigments, if incorporated at adequate concentrations and when properly dispersed in well-designed vehicles, not only add color to the lotion (or cream, powder, etc.), but contribute significantly to protecting the skin from many wavelengths of light.
Ultra-submicronized iron oxides protect against visible light waves, yet add little color to the finished product. This allows for the addition of higher levels of infrared protecting iron oxide while retaining the cosmetic elegance and shade of the final preparation. Considerable blocking of ultraviolet rays is also reported with submicronized iron oxides, complementing further the primary UV blocking agents.
Indirect Physical Blocker Aids
Examples of these particles can be natural talc or mica. They are usually flat and oval in shape. They are very small particles, though they are much larger than direct physical blockers. A portion of very small physical blocker particles will coat the larger flat talc (mica, etc.). Being flat and smooth, the coated particles of talc easily slide over each other, overlapping themselves and effectively increasing protective coverage on the skin.
Polymers can be natural substances from plants, modified semi-natural, animal derived substances (modified chitin, from the “shells” of shrimp etc. is commonly employed) or synthetic substances such as micronized nylon. Certain polymers, when carefully formulated into a photoprotective preparation, create a maze–like “cage” structure that forces the ultraviolet and visible rays (100nm–760nm) to go through a “maze” rather than reaching the skin directly. This longer route helps to protect the skin from these rays by preventing some rays from reaching the skin, by causing some rays to reach the skin after some of their energy has dissipated, and by increasing the contact time between the rays and the organic filters/physical blockers. By themselves, such polymers (which incidentally also improve the feel of the cosmetic finished product on the skin) do little to provide skin photoprotection. They help to defend the skin from wind and wind-blown dirt and grime pollution particles. However in the presence of active photoprotective agents, these polymers can increase the Sun Protection Factor (SPF) by three to five points.
CHEMICAL ABSORBERS/ORGANIC FILTERS
Chemical Sunscreens (also known as Organic Filters) are usually soluble in oils or water. These filter either/or UVB and UVA irradiation to varying degrees of efficiency. No organic filter completely blocks the UVB and/or UVA rays from the skin. Further, the actual protection offered by any and all sun-protective products relates directly to their level of concentration: the thickness of the film applied to the skin, as well as the careful, total coverage of the exposed skin sites.
The most common chemical absorbers used in sunscreens include:
Octyl Salicylate - Salicylates are the oldest class of sunscreens, with octyl salicylate the most widely used. While it is strictly a UVB absorber, and a weak one at that, it offers several positive qualities, including:
• Octyl salicylate is virtually nonirritating and nonsensitizing to skin.
• Cosmetically, octyl salicylate is an easy to handle emollient “oil” that acts as a good solvent (solubilizer) for other, solid organic sunscreens, such as the benzophenones.
Octyl Dimethyl PABA (Padimate O) - This oil-like UVB absorber is the most efficient for this ultraviolet range. It absorbs best at the maximum sunburn frequencies (310nm–312nm). It had been the most popular UVB sunscreen in the United States, but adverse reports (not necessarily proven) have reduced its use. Padimate-O is a PABA derivative, but quite distinct. Today’s purified material is essentially free of PABA.
Octyl Methoxycinnamate - Currently, this oily liquid is the most widely utilized organic UVB absorber used in the world. It is second in efficiency to Padimate-O, yet offers broader protection (300nm –315nm) in the sunburn region of UVB. It has a very good safety record and is relatively easy to formulate. Additionally, it is moisturizing and water insoluble, adhering tenaciously to the skin.
Menthyl Anthranilate - An old and safe, yet overall weak, absorber. Menthyl anthranilate absorbs moderately in the UVB range from about 300nm and somewhat more strongly into the UVA (up to about 340nm). It can somewhat enhance the UVB and lower (320nm to 340nm) UVA absorption of more active absorbers.
Oxybenzone (Benzophenone-3) and Sulisobenzone (Benzophenone-4) - These are closely related solid (powder) absorbers. Oxybenzone is water–insoluble, yet the acid form, sulisobenzone, can be made soluble in water when it is neutralized. While these compounds are classified as UVA absorbers they are also UVB absorbers. Overall, they offer only moderate protection through both the UVB range and part of the UVA (320nm – 360nm). They are quite stable and can enhance effectiveness of stronger UVB absorbers.
Avobenzone (Parsol®1789) - This solid (powder) absorber exhibits marginal UVB and lower (320nm – 330nm) UVA absorption. It provides good UVA absorption from about 330nm to 340nm and very good absorption in the UVA range up to about 370nm. At that level, it rapidly loses effectiveness. Because of its irritation potential, it is only permitted to be used in low concentration levels. Accordingly, this limits the actual level of protection obtainable. In addition, in the presence of sunlight, avobenzone can convert to its inactive form and readily loses more than one-third (1/3) of its active form rather quickly. Therefore, avobenzone (Parsol 1789) has useful, yet limited, UVA protection. Its usefulness can be enhanced by combining with UVB absorbers and physical protectors, such as zinc oxide.
Octocrylene - An emollient, water resistant UVB/UVA absorber. While octocrylene is a relatively weak sunscreen, it gives some protection in the UVB and lower (320to 350 nm) UVA range. Most importantly, octocrylene is a very stable absorber and both protects and augments other UV absorbers, and also improves their ability to provide a uniform coating of the skin.
The history of incorporating ultraviolet light filters into personal care products has grown enormously. This is due to both an increased awareness of the damaging effects of ultraviolet radiation on the skin, and a desire to build market presence based on a consumer driven demand.
Unfortunately, the traditional rating system utilizing SPF (sun protection factor) is not acceptable as a true measure of protection from the long-term effects of ultraviolet damage, since it fails to incorporate the damage as a result of the ultraviolet A wavelength. Currently, multiple FDA approved UVA active ingredients are marketed, and a new UVA chemical filter has recently received FDA approval, while others await the FDA’s evaluation. Yet it is not until a final FDA approved document exists that clarifies the complicated UVA rating system, that we will be able to truly determine a products level of UVA protection.
Dr. Harry Fallick has been involved in the clinical treatment of skin cancer for over twenty years. As a triple board certified surgeon, he developed a special interest in the treatment of photo damaged skin. Since founding Fallene, Ltd. in 1989, he has focused his attention on the development of ultra protective full spectrum sunscreens.