Choosing Appropriate Sunscreens: Why Ingredients

To preserve their health and the appearance of their skin, patients need  straightforward advice about product selection.

 By Robert T. Buchanan, MD

Every medical aesthetician recognizes that sun protection plays an integral role in any patient’s efforts to rejuvenate the skin. From those who pursue topical anti-aging regimens alone to those who undergo laser resurfacing, patients cannot hope to maintain beneficial effects unless they avoid future sun damage. But the importance of sun protection goes far beyond preserving a youthful appearance. By protecting against UV-induced cell damage and cutaneous malignancy, appropriate sun protection plays a crucial role in preserving skin health as well as the individual’s overall wellbeing.

“The notion of UVA safety couldn’t be further from the truth. Both UVA and UVB are harmful to cells and put patients at risk for skin malignancies. Use of tanning beds has been shown to increase the risk of developing skin cancer by up to 250 percent.”

Unfortunately, too few patients understand or practice adequate sun protection, and, despite their well-meaning precautions, many actually put themselves at higher risk for sun damage and skin cancer development. Below, I’ll describe appropriate sun protection and highlight key elements of patient education.

Understanding UVR

Conventional wisdom holds that UVA contributes significantly to aging w h i l e U V B produces burns. The scientific design a t i o n s conveniently reiterate the association: A for aging; B for burn. Although, growing scientific evidence proves these tenets are basically correct, they are woefully oversimplified. Though this has been known for some time, the difference has all but been ignored, probably because of our previous inability to block anything effectively except UVB.

UVB radiation has a relatively high energy, but is easily blocked by the atmosphere, glass, clothing, and the skin. UVB levels vary based on time of day, season and location, and the energy is nearly non-existent at night. Because the atmosphere absorbs UVB rapidly, energy levels on the earth’s surface are relatively low compared to UVA. In the winter in the Midwestern US, the UVB level is approximately five percent. In South Carolina in the summer, levels are double that, at about 10-12 percent. UVB radiation penetrates only the superficial epidermal layers, where the absorbed energy produces redness and heat and can cause cellular damage that may lead to skin cancer.

By contrast, UVA radiation, which is minimally absorbed,is much more abundant, with minimal variability by time of day, season or locale. In North Dakota in the winter, roughly 88 percent of UVA radiation reaches the earth. In the summer in South Carolina, those levels top out near 94 percent, just six percentage points higher. And, though many people don’t realize it, UVA levels remain high at night. Therefore, the traditional time to avoid the sun (10am to 2pm in summer) is not really applicable, and should no longer be advised except to reduce the chance of sunburn. Unlike UVB, UVA radiation penetrates deeply. It penetrates through most clothing and penetrates deeply into the epidermis and dermis.

Because of incomplete or inaccurate understanding of the roles of UVA and UVB, the public has been led to believe UVA is somehow “safer” than U V B ; many tann i n g b o o t h s used to boast that they used UVA only. This notion of UVA safety couldn’t be further from the truth. Both UVA and UVB are harmful to cells and put patients at risk for skin malignancies. In fact, use of tanning beds has been shown to increase the risk of developing skin cancer by up to 250 percent.9

UVA has long been associated with melanoma risk,4 though the mechanism remains unclear. But since melanoma is the rarest form of skin cancer and is associated with genetic and other health risks, many underplayed the risk. However, recent research suggests that UVA also plays a major role in development of squamous cell carcinoma and basal call epithelioma, the two more common types of skin cancer.3 We also know that beyond causing direct damage to cells, UVA radiation can cause a significant degree of indirect damage through free-radical generation (see below).

 The Trouble with SPF

A better understanding of the effects of both UVB and UVA has prompted a growing number of medical aestheticians to recommend broadspectrum sun protection—against both UVA and UVB—for all patients, but most don’t give patients the right advice. The commonly accepted recommendation is daily application of a broad-spectrum sunscreen with an SPF 15 or higher.

This simplistic directive is a tremendous disservice to patients. In reality, the notion of SPF is outdated and of little value. The sun protection factor represents the level of protection from burning a particular product provides based solely on protection from UVB rays. It does not account for UVA.5 Furthermore, the numeric SPF rating system is misleading. A product with SPF 15 may block about 90 percent of the UVB radiation an unprotected individual would encounter. In South Carolina, a patient using SPF 15 sunscreen would be protected from all but about one to two percent of UVB radiation reaching their skin.

Patients often mistakenly assume that using a product with SPF 30 means double the protection of SPF 15, either in terms of amount of radiation blocked or duration of effect. In actuality, doubling the SPF from 15 to 30 may boost the amount of blocked UVB from 90 percent to about 94 percent. Although higher SPF products are supposed to increase the time one can stay in the sun without burning, this does not translate to increased longevity of effect. The duration of effect of any product depends entirely on the ingredients and the formulation, particularly its water/sweat-proof rating, and the way it is used.

Overemphasis of SPF coupled with incomplete understanding of it has produced a false sense of security among sunscreen users and likely led to increased cumulative UVA exposure for well-intentioned but misguided patients.

Ingredients are Key

The most accurate, straightforward advice that any professional can give patients is not the standard “daily, broad-spectrum, SPF 15 or higher.” It’s imperative to promote broad-spectrum coverage, but there’s no need to address SPF. It’s more appropriate to educate patients how to practice sun avoidance and physical skin protection (with protective clothing and accessories, see below) and to direct them to appropriate products that offer effective broad-spectrum protection. This means a sunscreen product that contains zinc oxide (ZnO) at least 3.5% or higher.

While a few other effective ingredients are available overseas and in Canada, the only ingredient available in the US that provides very good full-spectrum, practical protection against UVA and UVB is zinc oxide or Z-Cote. Micronized zinc is incorporated into many cosmetic products as a coloring agent, but it has important sun-protective properties. Cosmetics containing zinc oxide actually protect the skin from sun damage, whereas those advertising an SPF rarely actually protect from anything other than burning.

Zinc oxide is a physical sunscreen—it sits on the skin rather than permeate through it, as chemical sunscreens do. The zinc particles create a reflective barrier that deflects UV radiation away from the skin. Most important, micronized ZnO goes on clear and is, therefore, practical. Products with 3.5% or more Z-cote usually incorporate other sunscreens for excellent UVB/UVA protection.

Zinc oxide is a practical, patient-friendly ingredient; it is very water resistant. Once applied, it will remain on the skin and remain active until it is washed off. Therefore, a patient who applies a Z-cote-containing sunscreen each morning will enjoy full-spectrum protection throughout the day. A patient who swims, perspires significantly, showers, etc., obviously requires reapplication.

I consider any additional ingredients a bonus that may enhance or augment the effect of ZnO. Like ZnO, titanium dioxide (TiO2) is a broadspectrum physical sunblock ingredient, but it is less effective against UVA since it does not protect from the longest wave radiation. Even as a microfine particle, TiO2 may produce a whitish residue, and it is often difficult to formulate a cosmetically acceptable sunscreen product using it alone. However, in combination with ZnO, TiO2 may produce a cosmetically acceptable product. Because they are inert and sit on the skin, neither agent produces allergic reactions.

Parsol 1789 or avobenzone is a chemical sunscreen that can very effectively absorb UVA radiation and is often used in combination with traditional UVB blockers to provide full-spectrum protection. While Parsol is proven effective at blocking UVA, it is impractical because it degrades upon exposure to sunlight. The ingredient is active for only about 60-90 minutes from the time of application and must be reapplied thereafter. Most people will not keep it on enough to offer real protection.

Micronized zinc, titanium dioxide, and avobenzone are the most popular UVA-blocking sunscreen ingredients. Oxybenzone also blocks some shorter wave UVA radiation.

A number of UVB-blocking chemical sunscreen ingredients (absorbed through the skin) are also commonly used today in place of PABA, the grandaddy of chemical sunscreens. PABA is an effective UVB filter, but it is not cosmetically elegant and adverse reactions were common, leading to its general abandonment. Octyl methoxycinnamate is probably the most common chemical for UVB protection. It is very effective and is frequently combined with less powerful UVB-absorbing agents.

The Cover-Up

Zinc oxide’s status as a physical rather than chemical sunscreen is one of its greatest strengths. However, a topically-applied sunscreen should never be the patient’s sole method of sun protection. Patients must adopt additional physical protective measures. Patients require specific, straightforward instruction on sun avoidance and protection strategies. Remember, UVA is penetrating, and the radiation can pass through most standard fabrics. It is also ubiquitous. If you can read a book without a light, you are in UVA radiation.

In recent years, a number of companies have developed sun-protective clothing lines. Specially-woven and treated fabrics that reflect both UVA and UVB radiation are used to make swimsuits, everyday clothing, and hats. The Rit Dye Co. now makes a product (Sun Guard) that washes UV protection into regular clothes for about six months.

Patients who spend any time outdoors, in the car, or near windows should consider such clothing. Even umbrellas and canopies can be made from these UVR-reflecting materials. Additionally, patients must apply their Z-cotecontaining sunscreen to all uncovered areas at least once daily and re-apply as needed. Note that the hands, ears, back of the neck, and often the feet (especially when women and men wear open shoes) require application of sunscreens but frequently go overlooked.

Adjunctive Ingredients

When UV radiation penetrates the epidermis, it can cause direct cellular damage. However, it can also have indirect effects through formation of oxygen free radicals that ultimately attack other healthy cells. Antioxidants incorporated into either sunscreens or other topical skin care products can seek out free radicals and neutralize them.

Numerous antioxidants are formulated into topical skin care products. Data demonstrate their effectiveness, but the benefit of any particular product depends on the quality of the active ingredient and the overall formulation. Generally, trusted, national manufacturers will have products with the highest levels of active ingredient.

Zinc itself may be an important antioxidant for cutaneous health. In addition to religious use of Z-cote-containing sunscreens, I recommend use of topical products containing vitamin C (Lascorbic acid), such as Obagi Cffectives Serum. Besides being an antioxidant, L-ascorbic acid has the added benefit of being anti-inflammatory.

Studies show that topically applied vitamin C can actually reverse damage, contributing rejuvenating effects. Several topical vitamin C formulations are available.

Three and Clear

We cannot avoid sun exposure. We must learn to protect ourselves. Patients who adopt a simple regimen of:

•  wearing sun protective clothing and hats when going outdoors,
• applying a sunblock containing zinc oxide 3.5% or higher to all sun-exposed skin every day,
•  applying topical antioxidant vitamin C to the face and sun-exposed skin will tremendously reduce their risk of damage from UVB and UVA rays and help their bodies actively fight and repair damage caused by UVR.

Long-term benefits include reduction in visible signs of sun damage (such as dermal thinning, thickening of the dead cell layer, wrinkling, texture change, and pigment irregularities), better overall skin health, and lower risk of skin malignancy.