Our Blog

Skin Cancer Prevention by Craig J. Eichler M.D.

Posted on April 15, 2015

May is national Skin Cancer Awareness Month and for my first ever blog posting I get to write about something that I am passionate about: the prevention of skin cancer.

To appreciate the enormity of the problem with skin cancers here are a few statistics to show why dermatologists say we are facing a skin cancer epidemic.

1. Skin cancer is the most common form of cancer in the United States. More than 3.5 million skin cancers in over two million people are diagnosed annually.
2. Each year there are more new cases of skin cancer than the number of cancers of the breast, prostate, lung and colon combined.
3. One in five Americans will develop skin cancer in the course of a lifetime.
4. In the US, one person dies every hour from skin cancer.

The bad news is that skin cancer rates have been increasing over the years. The good news is that with appropriate sun protection you can greatly lessen your risk of developing skin cancer.

So, what can you do to decrease your risk of developing skin cancer? The one risk factor we can control is how we protect ourselves from the sun. The sun emits ultraviolet light, which is believed to be the single biggest trigger of skin cancer. Ultraviolet light is part of the spectrum of light our sun emits, is divided into Ultraviolet B (UVB) and ultraviolet A (UVA). UVB is associated with sunburns and UVA with tanning and aging appearance. Although UVB is more potent, both UVB and UVA exposure can increase risk of skin cancer.

Ways to decrease ultraviolet exposure include:

1. Avoidance
2. Clothing
3. Sunscreens

For many, sunscreens are the mainstays for sun protection. Although sunscreens play an important role in sun protection; they have limitations. It is these limitations, which I will elaborate, that lead to the misconception that as long as you applied sunscreen you are protected. You will see that rather then being the main method of sun protection; sunscreens are best used as an adjunct or additional means of sun protection. For that reason, I put it 3rd on the list above as measures we should take to protect.

Next, lets review some important aspects of sunscreens: what they do and don’t do well.

Sunscreens contain ingredients, which either absorb or reflect ultraviolet rays. The SPF number is the most recognized feature of the sunscreens effectiveness. The SPF represents a measure of UVB protection and is based on how much longer it would take to develop sunburn. For example, applying an SPF 2 sunscreen should make it twice as long to get sunburn. You may have read else or been told that SPF higher then 15 isn’t necessary since you get very little added protection using ultra high SPF numbers. After all, an SPF15 which block about 93% of UVB and a SPF 30 about 97%. So why would dermatologists recommend SPF 30 or higher when there appears to be relatively little added protection compared to SPF 15? Here’s why:

1. If we look at the SPF another way; instead of saying that SPF 15 blocks 93% of UVB, the SPF 15 sunscreen allows about 7% of UVB to get through. A SPF 30 lets about 3.5%; so it is still blocking twice as much as the SPF 15.
2. Most people apply their sunscreens too sparingly; on average less then half the amount that is needed to get the SPF that is on the label. The SPF on the label is based on applying so that there is 2 mg/cm2 thickness of sunscreen product. So instead of getting an SPF 15 the average person applies an amount that gives them an SPF 8 or less. Using a high SPF sunscreen may offer you some margin for error if you under apply. So, how much does it take to get to the recommended thickness? About an ounce for the exposed body area. That is about a quarter of a 4 oz bottle. I recommend to use a teaspoon of sunscreen for the face, ears, and neck; a teaspoon for each arm, and each leg, one for the back and one for the chest and belly.
3. Sunscreens wear off. If you are swimming or sweating, the sunscreens lose their effectiveness over time. The sunscreens labeled “water resistant” (maintains protection for 40 minutes in water) or “very water resistant” (maintains protection for 80 minutes in water). There is no true “water proof” sunscreen that doesn’t wear off. And if you don’t see “water resistance” at all then the protection after sweating or swimming may be minimal.

For each of these reasons a sunscreen with SPF 30 or higher can offer valuable more protection then lower SPF sunscreens.

As mentioned earlier the SPF is based on UVB protection. But what about UVA protection? UVA protection is also very important to avoid damage, particularly aging appearance of the skin such as wrinkles, coarseness, and brown spots. In fact it is believed that 90% of aging appearance of the skin is due to sun exposure. More recently studies also show that UVA exposure is important risk factor for developing skin cancer, particularly melanoma. Besides the sun, tanning beds emit these damaging UVA rays. So despite tanning bed industry’s claim that use of their tanning beds is safe; UVA is a proven carcinogen. Tanning bed use can be deadly.

There are several ingredients in sunscreen that offer UVA protection. You should look for a sunscreen, which contains at least one of the following UVA blockers: Zinc oxide, titanium dioxide, avobenzone, or ecamsule (Mexoryl).

When asked which is the best sunscreen, I tell patients it’s the one that you actually will use! I then remind them of these parameters: ideally one that has an SPF at least 30; strong UVA blocking ingredients, and apply generously and reapplied every 2 hours.

I want to emphasize that sunscreens are helpful but they don’t block all the UV light and therefore they are not the end all of sun protection you should use.

My next post will discuss more about importance of clothing and tips for avoidance of UV exposure.

Written by:
Craig J. Eichler, M.D.