The primary, preventable cause of aging is exposure to UVB/UVA radiation. Repeated ultraviolet exposure produces photoaging of the skin, which differs from the intrinsic aging process of the skin that is dependent on genetics and chronologic age. Photoaging is characterized by rough skin texture, dilated pores, poor skin tone, skin laxity, blotchy skin color, brown spots, sallowness, telangectasia (sometimes called broken blood vessels), fine lines, and wrinkles.1,2
The ubiquitous nature of ultraviolet rays requires the use of sunscreen agents to block the damaging effects. Since UVB (280-320nm) and UVA (320-400nm) radiation contribute to photoaging, it is important to provide UV protection over a broad spectrum of ultraviolet radiation (280-400nm). (Table 1) To provide this type of protection, a sunscreen must contain a combination of organic (chemical sunscreen ingredients) and inorganic (physical sunscreen ingredients) filters. Combination sunscreens enhance the SPF of the final product.
It is important for all medical-affiliated personnel (physicians, nurse practitioners, chiropractors, physician assistants, nurses, aestheticians, physician office staffs, and all those medical-associated specialists not listed) to understand the science and benefits of sunscreens in order to better educate their patients, clients, friends and family about the importance of UV ray protection.
Types of Sunscreens and SPF
Chemical sunscreen ingredients act as an ultraviolet sponge to absorb damaging UV rays. This chemical reaction creates heat, and some patients may state that they feel hot when out in the sun with a sunscreen applied. This feeling of warmth is not intense or harmful but is created by the chemical reaction of the UV rays with the chemical sunscreen ingredient. Physical sunscreen ingredients deflect or block damaging UV rays in a similar fashion to protective clothing. Current toxicology based on acute and chronic exposure to (UVB/UVA) broad spectrum sunscreens concluded that sunscreen ingredients or products pose no human health concern despite any remarks to the contrary that appeared in a recent Allure magazine article and comments made by the Environmental Working Group.3 In addition, micronized, transparent zinc oxide is not absorbed into the skin, and there are no reports of skin allergies to zinc oxide.
Misleading remarks made in the media regarding the safety, efficacy and benefits of sunscreen ingredients and the use of sunscreen could unfortunately lead people to stop or decrease their use of sunscreen agents. Most dermatologists would agree that the use of sunscreen has attributed to a decrease in the incidence of photodamage and pre-cancerous skin lesions. In fact, the American Academy of Dermatology recommends that, regardless of skin type, a broad spectrum sunscreen with an SPF of at least 15 should be used year-round. Patients must understand that sunscreen shouldn't be reserved for use only on sunny days. Even on a cloudy day, up to 70 percent of the sun's ultraviolet rays can pass through the clouds. Additionally, sand reflects 25 percent of the sun's rays, and snow reflects 80 percent of the sun's rays.
SPF is an indication of a sunscreen's effectiveness preventing sunburn related to the length of time in the sun, but it does not actually increase proportionately absorbing the damaging UV rays. An SPF of 35 blocks 97-98 percent of the UVB rays, while a SPF of 15 blocks 93 percent of the rays, and an SPF of 2 screens 50 percent of the UVB rays (Table 2). The take away for sun protection: a SPF of at least 15 should be used on a daily basis and there is not much extra protection for a product with an SPF greater than 35.
The SPF only relates to a sunscreen's ability to block UVB rays. Unfortunately, at the present time there is no measure to quantify the effectiveness of a sunscreen's ability to block UVA rays. It is well known that chemical sunscreen ingredients that block UVA rays are somewhat unstable when exposed to UV rays and oxygen (air). This is further complicated by the fact that we do not have the ability to measure the stability or effectiveness of chemical sunscreens that block UVA rays. It should be obvious that the most reliable and effective ingredient for protecting the skin from UVA rays are physical sunscreen ingredients. Zinc oxide and titanium dioxide are the two physical blockers used in the United States. In the past, the use of physical blockers posed cosmetic problems, as the skin looked like it was covered by a white paste. Nanotechnology has eliminated this problem by creating micronized particles of zinc oxide and titanium dioxide. Micronized zinc oxide and micronized titanium dioxide are transparent when applied to the skin.
The ideal sunscreen must be broad spectrum, that is, containing agents that can provide protection from both UVB and UVA radiation. The product needs to be cosmetically acceptable to enhance use and compliance. All FDA-approved sunscreen ingredients have a particular absorption spectrum. The ideal sunscreen would combine ingredients to expand the range of ultraviolet protection from damaging ultraviolet rays and should include either micronized zinc oxide or titanium dioxide, given the lack of knowledge regarding the effectiveness of chemical UVA blockers.* In addition, it has been shown that daily use of a sunscreen increases its photoprotection, as sunscreen ingredients can bind to skin cells in the outer layer of the skin. Bottom line: combination sunscreens with adequate SPF, containing micronized zinc oxide or titanium dioxide, and used with daily application increase a sunscreen's ability to neutralize UV rays.
Formulation Considerations and Controversies
Most sunscreens are highly effective for preventing sunburns and will decrease the chance of the skin turning red or becoming irritated from the heat of the sun. Certain sunscreens can actually cause negative cutaneous effects due to the incorporation of irritating or allergenic ingredients.4 Some of these negative effects include, but are not limited to, dryness of the skin, allergic dermatitis, irritant dermatitis, photosensitivity, and acne, while some reports attribute cancer and skin aging to poorly formulated products. With some brands of sunscreen, even mere inhalation of the product can cause reactions in some patients. It is important to find the right sunscreen for each person and to ensure that these symptoms do not occur with the brand they are using. Sunscreen should not be applied to children under six months of age, who are best not exposed to direct sun, anyway.
Studies have found that the incidence of skin cancers has increased even as sunscreens have become popular among fair-skinned people. The establishment's answer to this increase in the cancer rate is that wearing sunscreens makes people stay in the sun too long. A study by Drs. Mike Brown and Philippe Autier (European Institute of Oncology in Milan) reported that children using sunscreen returned from holiday with more nevi5—a possible sign of increased cancer risk. Some say that people who wore higher factor sunscreens tended to stay out in sunlight much longer, because they felt protected.6 However, others have pointed out that if sunscreen chemicals were protective, the factors of longer sun exposure would be somewhat countered by the sunscreen's “supposed” protective actions.
Over the past decade, the Environmental Working Group (EWG) studying cancer has come to an unsettling conclusion; that is, they believe the use of sunscreen chemicals may actually be increasing the incidence of cancer and that sunlight exposure may decrease human cancer rates and improve a person's health.
The organization is concerned that many heavilyused, chemical sunscreens actually increase cancers by virtue of their free-radical-generating properties. And more insidiously, they suggest, many commonlyused sunscreen chemicals have strong estrogenic actions that may cause serious problems in sexual development and adult sexual function and may further increase cancer risks; but it is important to really look at the evidence.
The fact is there are no published human studies on the cancer-causing potential of retinyl palmitate,7 a prime focus of the EWG. There are, however, observations from decades of clinical practice that do not support the notion that retinyl palmitate in sunscreen causes or promotes skin cancer.7
Most chemical sunscreens contain UVA and UVB blockers in concentrations that range from 2-6%. There are claims that UV rays cause some sunscreen ingredients, such as Benzophenone (and similar compounds), to break down, creating damaging free radicals. Many sunscreens also contain triethanolamine, a compound that is suggested to cause the formation of cancer-causing nitrosamines in products by combining with nitrite used as a preservative and often not disclosed on product labels.
There is another claim that sunscreen chemicals have estrogen-like effects.8 Such effects can increase cancers, cause birth defects in children, lower sperm counts and penis size in men, plus a plethora of other medical problems. Estrogenic chemicals can mimic hormonal (or real) estrogen, the key female sex hormone. When the body's hormone receptors recognize the estrogenic chemical as estrogen, the result is feminization of the tissue.
Concerns brought about by earlier scientific studies have led authorities in the EU to regulate that any sunscreen product containing a more than 5 percent dose of oxybenzone should be labeled accordingly. Benzophenone (benzophenone-3), homosalate, and octy-methoxycinnamate (octinoxate) are troubling, because they have shown estrogenic activity in lab tests.9 Oxybenzone is a derivative of benzophenone, and it is linked to allergies, hormone disruption, and cell damage.10 However, most studies looked at very high doses of these drugs. According to reports,11 the Centers for Disease Control (CDC) say that 97 percent of Americans are “contaminated” with this widelyused sunscreen ingredient. The study in question did find evidence of the chemical in nearly 97 percent of analyzed urine samples, though the source of exposure was not assessed by the investigators.12
Parabens (butyl-, ethyl-, methyl-, and propyl-) are common in sunscreens, so avoiding them may prove difficult. They are preservatives that have estrogenic qualities. They have also been found to accumulate in the breast tissue of women with breast cancer.13 However studies fail to show a direct connection between topically applied parabens and human disease or interference with endocrine function.14
While on the surface of the skin, the chemicals Padimate-O and Parsol 1789 (Avobenzone) appear to prevent UV damage, but when absorbed into the skin, it has been suggested that they can actually damage DNA. There are suggestions that the sun's light may cause these chemicals to become reactive and cause free-radical damage when they're absorbed.
In general, zinc oxide and titanium dioxide are good sunscreen choices as they scatter or reflect the sun's rays rather than absorbing them. However, traditional sunscreen formulations are not absorbed into the skin (thus the white streaks on the skin), so there is less risk of organic substances building up in the body.15 Some of the studies suggesting negative effects of sunscreen chemicals included excessive doses and systemic exposures, but overall, there is no good evidence to suggest that topical use of sunscreens is toxic to humans.16
A Role for Antioxidants
Ultraviolet rays create free radicals that cause photoaging of the skin. It has been demonstrated that the skin's native antioxidant protection breaks down during excessive UV injury and aging (due to the fact that there are more free radicals created by the UV damage and cell metabolism than there are antioxidant molecules available in the skin). This allows free radicals (reactive oxygen species) to damage (nucleic acids) DNA, proteins, and lipids.17
The photoprotective capability of antioxidants does not lie in their ability to reflect or absorb UV rays. Rather, they prevent the damage created by UV-generated free radicals.17,18 Antioxidants neutralize free radicals by donating one of their own electrons, ending the destructive cascade. The antioxidants themselves don't become free radicals, because they are stable in either form due to their chemical behavior. They act as scavengers to prevent cell damage. Antioxidants that give up their electrons are not harmful, because they have the ability to accommodate the change in electrons without becoming reactive.
Under normal conditions the antioxidant defense system within the body can easily handle free radicals that are produced. During times of excess free radical production, lipid peroxidation occurs. A free radical attack on a membrane usually damages a cell to the point that it must be removed by the immune system. Free radicals are commonly associated with an inflammatory response and are hypothesized to be greatest 24 hours after an insult. The immune system is the main body system that utilizes free radicals.
New methods to protect skin from photodamage are necessary, as sunscreens are under-used and have incomplete spectral protection. Skin naturally uses antioxidants to protect itself from photodamage. Vitamin C, Vitamin E, alpha lipoic acid, retinol, selenium, zinc, solymarin, soy, soflavones, and tea polyphenols may supplement sunscreen protection and provide additional photodamage repair when sunscreens fail.17-19 Photochemical reactions occur in the skin when UV rays are absorbed by the DNA of the cell (a chromophore) causing a series of photochemical reactions. Oxidation reactions can damage nucleic acids, proteins and lipids. Oxidative damage is cumulative. UVB (280-320nm) damage causes cyclopyrimidine dimers, especially thymine dimers (body has nucleotide excision repair of damage if not too excessive). Cells are equipped to repair oxidative damage with enzymes including catalase, glutathione reductase, and glutathione peroxidase, which collectively destroy hydrogen peroxide and lipid hydro peroxides. In addition, superoxide dismutase destroys superoxide. Non-enzymatic antioxidants include glutathione and ascorbic acid in the water phase and Vitamin E and ubiquinol in the lipid phase.
A few antioxidants are Vitamin A, Vitamin C, Vitamin E, alpha lipoic acid and minerals (selenium). Antioxidants are manufactured in the body and can also be applied to the skin or extracted from ingested food. In other words, they create an increase in photoprotection when used in conjunction with sunscreens, such as Rx Systems PF's Facial Moisturizer SPF 35 with transparent zinc oxide.
Patients must be counseled that there are other things that can be done in addition to wearing an effective sunscreen to protect against UVA/UVB rays. Particularly if they are reluctant to wear sunscreens or are simply non-compliant, patients should be encouraged to wear protective clothing, find shade, avoid tanning beds, and get Vitamin D safely. These are all effective tools with which dermatologists are familiar but bear repeating to patients.
There is some natural protection from the sun's damaging rays, but it is not sufficiently protective in itself. The ozone is the major photoprotective agent in the atmosphere. It is thickest at the north and south poles and is thinnest at the equator. Ultraviolet ray intensity increases about 10% with every 1,000 feet of elevation above sea level. Denver, the Mile High City, is 5,280 feet above sea level and has a higher intensity of UV rays due to it altitude versus New Orleans which is at sea level. Snow, ice, sand, glass and metal reflect UV rays. UV rays are able to penetrate water to a depth of about 30 inches. It is important to remember that fog and clouds only reduce UV intensity about 30 percent, and the sunscreen benefit of clothing is related to the thickness, type of fiber, weave, stretch, color and other factors. In fact, nylon stockings have a SPF of only 2-3.
Patients often inquire about window glass and sunglasses. UVB rays are blocked by glass, but UVA rays (the longer wavelength UV rays) pass through window glass and sunglasses and can damage the skin and eyes.
Well-formulated, Safe Sunscreens are Worthwhile
All the news is not bad. There have been advances. Environmental regulations have improved the thickness of the ozone layer. Clothing has been manufactured to provide sun protection, some chemically treated with sunscreen agents. Glass has been thickened, polarized and tinted to increase its sun protective properties. Many cosmetic products also contain pigment and sunscreen ingredients, which increase their sun protection ability to a SPF 3-15 based on the product.
Inorganic sunscreens—micronized zinc oxide and titanium dioxide—provide broad spectrum protection with no concerns about toxicity. Organic sunscreens, despite some troubling and frequently over-emphasized theoretical concerns, have not been shown to induce cancers or harm patients when used as directed. The incorporation of antioxidants into sunscreens provides added protection against the harmful effects of UV exposure and may provide reparative effects if/when sunscreens fail. Emphasis on inorganic sunscreens and synergistic antioxidants may avoid concerns associated with organic sunscreens and may be particularly useful for the patient with concerns about specific sunscreen ingredients. As a sunscreen formulator, I have reviewed the evidence and determined that an optimal sunscreen formulation must contain a combination of broad-spectrum sunscreen ingredients, antioxidants, and skin conditioning agents to enhance the SPF of the final product, especially with everyday use.
Dr. Samuels recently developed a new Rx Systems PF® Facial Moisturizer with SPF 35 created as the ideal sunscreen for everyday use. The new facial moisturizer with SPF 35 provides a broad spectrum UVB/UVA protection in a facial moisturizer appropriate for all skin types. It combines four sunscreen ingredients to expand the range of ultraviolet ray protection including transparent, micronized zinc oxide which leaves no filmy, white residue. Antioxidants are incorporated to enhance its photoprotective properties. The Rx Systems PF facial moisturizer is PABA-free, non-comedogenic, non-greasy, and light-weight.
It is important for all medical-affiliated personnel to understand the science and benefits of sunscreens in order to better educate their patients, clients, friends and family about the importance of UV ray protection. Misleading remarks in the media regarding the safety, efficacy and benefits of sunscreen ingredients and the use of sunscreen could unfortunately lead people to stop or decrease their use of sunscreen agents. Inorganic sunscreens—micronized zinc oxide and titanium dioxide—provide broad spectrum protection with no concerns about toxicity. Organic sunscreens, despite some troubling and frequently over-emphasized theoretical concerns, have not been shown to induce cancers or harm patients or be toxic when used topically as directed. The incorporation of antioxidants into sunscreens provides added protection against the harmful effects of UV exposure and may provide reparative effects if/when sunscreens fail.