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When you buy sunscreen, the myriad of bottles and tubes jamming store shelves can leave even the savviest consumer puzzled. What’s the difference between UVA and UVB radiation? What’s behind those long, unpronounceable ingredient names? And does it really matter which sunscreen you buy?

UVA and UVB: Are You Protected?

Two types of ultraviolet radiation from the sun affect our skin: UVA and UVB rays. UVB rays are important for their role in helping the skin produce immunity-protecting vitamin D, but overexposure causes sunburn.

All commercial sunscreens contain active ingredients to protect against UVB rays. The sun protection factor (SPF) on a bottle of sunscreen indicates the level of protection the product provides compared to unprotected skin. Note that ultra-high SPF numbers are less meaningful. According to the American Cancer Society, a sunscreen labeled SPF 55 is less than two percent more effective than one labeled SPF 30. Higher SPF varieties may also contain more possibly harmful chemicals.

While all commercial sunscreens protect against UVB, not all block UVA rays. This form of radiation causes tanning more than burning and is linked to premature aging of the skin and skin cancer (J Invest Dermatol 2010; Epub). Sunscreens that offer UVA protection are often labeled “broad-spectrum”, although the level of protection is difficult for the consumer to determine since it is not reflected by the SPF value.

Active Ingredients

At least 30 different UV filter ingredients appear in commercial sunscreens.


Oxybenzone is readily absorbed into the skin — in fact, one of its roles in sunscreen is to enhance penetration of other ingredients. Centers for Disease Control studies found oxybenzone in the urine of 97 percent of people who used it topically. Oxybenzone is an endocrine disruptor, a chemical that acts like a hormone and disrupts normal hormonal functions (Environ Health Perspect 2008; 16:893-7). One study showed that fish exposed to oxybenzone had decreased reproductive ability (Aquat Toxicol 2008;90:182-7). This ingredient can also cause allergic reactions in some individuals.


Octinoxate has the benefit of being a low-allergenic UV filter. However, it is another endocrine interrupter. Multiple animal tests show that octinoxate decreases hormone levels, affecting thyroid function, sexual maturation, and reproduction (Toxicology 2007;238:192-9; Exp Clin Endocrinol Diabetes 2008;116:94-8).

Zinc oxide and titanium dioxide

Zinc oxide and titanium dioxide are minerals that act as physical blockers — they reflect UV rays away from the skin, unlike chemical blockers that absorb UV rays. They are touted as safe sunscreen options because they are not absorbed into the skin, and they very effectively protect against both UVA and UVB rays.

Many products use one or both of these minerals in the form of nanoparticles, microscopic particles developed to prevent the opaque white streaks of traditional mineral-based sunscreens. Such products may be labeled “clear zinc.” Researchers show mixed results on the safety of this cutting-edge technology.

Because nanoparticles are so tiny, some studies suggest that they could interact with and damage DNA (Toxicol Lett 2009;185:211-8). Scientists are continuing to learn more about the health implications of nanoparticles in sunscreen and other skin products.

Inactive Ingredients

Several ingredients common in skin products are also present in many sunscreens. Over 6,000 ingredients are used in modern cosmetics and skin care products. When considering the chemical load of all the products you use, including sunscreens, the doctor suggests particularly watching out for these ingredients:


Phthalates are a class of chemicals best known for their use in plastics, but they also appear in many personal care products under the guise of “fragrance”. Numerous studies have shown endocrine interruption in animals exposed to phthalates, and newer research implicates their impact on humans in such conditions as breast cancer and hindered fetal testicular development (Environ Health Perspect 2010;118:539-44; Folia Histochem Cytobiol 2009;47:S67-74).

Make a Smart Choice

Given the alarming research on so many common sunscreen ingredients, how can you and your family protect yourselves? First, be sure to get moderate sun exposure without sunscreen to ensure vitamin D production — this means enough sun to make the skin barely begin to turn pink but not begin to burn. (Anywhere from five to 30 minutes per day, depending on your skin and climate.) If you are going to be outdoors beyond that point, make shade, tightly-woven clothing and wide-brimmed hats your first line of defense.

When you do need to use a sunscreen, read labels carefully. Look for a broad-spectrum product free of phthalates (fragrances) and parabens, and use SPF values as general guidelines. Choose a mineral-based formulation over chemical blockers and apply it generously for full effectiveness, but only to skin that will be exposed.

If you do use a chemical-based sunscreen, reapply often since many of these active ingredients break down in the sun. Do not leave sunscreen outside or in the car for extended periods, as heat breaks down their effective ingredients.

To avoid inhalation risks, do not use spray or powder sunscreens. Finally, the doctor reminds patients that sunscreens do not prevent sunburn or skin cancer — they simply increase the time you can be in the sun before these risks kick in. Combine sunscreen use with common sense for the best results.

*Credit to Optimal Health University for the research and article.

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