Skin Cancer: Merkel Cell Carcinoma

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Causes, Risk Factors, and Prevention TOPICS

Can Merkel cell carcinoma be prevented?

The risk of getting Merkel cell carcinoma (MCC) is low, but there are things you can do that might help reduce your risk. These might also lower your risk of getting more common types of skin cancer, or even other types of cancer.

Limit ultraviolet (UV) exposure

The most important way to lower your risk of skin cancers (including MCC) is to limit your exposure to UV rays. Practice sun safety when you are outdoors. Simply staying in the shade is one of the best ways to limit your UV exposure. If you are going to be in the sun, “Slip! Slop! Slap! ®… and Wrap” is a catch phrase that can help you remember some of the key steps you can take to protect yourself from UV rays:

  • Slip on a shirt.
  • Slop on sunscreen.
  • Slap on a hat.
  • Wrap on sunglasses to protect the eyes and sensitive skin around them.

Seek shade

An obvious but very important way to limit your exposure to UV light is to avoid being outdoors in direct sunlight too long. This is particularly important in the middle of the day between the hours of 10 am and 4 pm, when UV light is strongest. If you are unsure how strong the sun’s rays are, use the shadow test: if your shadow is shorter than you are, the sun’s rays are the strongest, and it is important to protect yourself.

Keep in mind that sunlight (and UV rays) can come through light clouds, can reflect off water, sand, concrete, and snow, and can reach below the water’s surface, so protect your skin whenever you are outdoors.

The UV Index: The amount of UV light reaching the ground depends on a number of factors, including the time of day, time of year, elevation, and cloud cover. To help people better understand the strength of UV light in their area on a given day, the National Weather Service and the US Environmental Protection Agency (EPA) have developed the UV Index. It gives people an idea of how strong the UV light is in their area, on a scale from 1 to 11+. A higher number means a higher chance of sunburn, skin damage, and ultimately skin cancers of all kinds. Your local UV Index should be available daily in your local newspaper, on TV weather reports, online (www.epa.gov/sunwise/uvindex.html), and on many smartphone apps.

Protect your skin with clothing

Clothes provide different levels of UV protection, depending on many factors. Long-sleeved shirts and long pants or skirts protect the most. Dark colors generally protect more than light colors. A tightly woven fabric protects better than loosely woven clothing. Dry fabric is generally more protective than wet fabric.

Be aware that covering up doesn’t block out all UV rays. If you can see light through a fabric, UV rays can get through, too.

Some companies in the United States now make clothing that is lightweight, comfortable, and protects against UV exposure even when wet. These sun-protective clothes may have a label listing the ultraviolet protection factor (UPF) value – the level of protection the garment provides from the sun’s UV rays (on a scale from 15 to 50+). The higher the UPF, the higher the protection from UV rays.

Newer products, which are used in the washing machine like laundry detergents, can increase the UPF value of clothes you already own. They add a layer of UV protection to your clothes without changing the color or texture. This can be useful, but it’s not exactly clear how much it adds to protecting you from UV rays, so it’s still important to follow the other steps listed here.

Wear a hat

A hat with at least a 2- to 3-inch brim all around is ideal because it protects areas often exposed to intense sun, such as the ears, eyes, forehead, nose, and scalp. A dark, non-reflective underside to the brim can also help lower the amount of UV rays reaching the face from reflective surfaces such as water. A shade cap (which looks like a baseball cap with about 7 inches of fabric draping down the sides and back) also is good, and will provide more protection for the neck. These are often sold in sports and outdoor supply stores.

A baseball cap can protect the front and top of the head but not the neck or the ears, where skin cancers commonly develop. Straw hats are not as protective as ones made of tightly woven fabric.

Use sunscreen

Use sunscreens and lip balms on areas of skin exposed to the sun, especially when the sunlight is strong (for example, between the hours of 10 am and 4 pm). Sunscreens with broad spectrum protection (against UVA and UVB rays) and with sun protection factor (SPF) values of 30 or higher are recommended. Use sunscreen even on hazy days or days with light or broken cloud cover because UV rays still come through.

Always follow directions when applying sunscreen. Ideally, a 1-ounce application (about a shot glass or a palmful of sunscreen) is recommended to cover the arms, legs, neck, and face of the average adult. Protection is greatest when sunscreen is used thickly on all sun-exposed skin. Sunscreens need to be reapplied at least every 2 hours to maintain protection. Sunscreens can wash off when you sweat or swim and then wipe off with a towel, so they might need to be reapplied more often – be sure to read the label. And don’t forget your lips; lip balm with sunscreen is also available.

Some people use sunscreen because they want to stay out in the sun for long periods of time without getting sunburned. Sunscreen should not be used to spend more time in the sun than you otherwise would, as you will still end up with damage to your skin.

Remember that sunscreens are a filter – they do not block all UV rays. The sunscreen’s SPF number is a measure of how long it would take you to get sunburned, compared to how long it would have taken if you were not using it. For example, if you would normally burn after only 5 minutes in the sun, using a product with an SPF of 30 would mean you would still get burned in 150 minutes. And that’s assuming that you applied it as directed, which unfortunately many people do not.

Sunscreen can reduce your chance of getting skin cancer. But there’s no guarantee, and if you stay in the sun a long time, you are at risk of developing skin cancer even if you have applied sunscreen.

Wear sunglasses

Wrap-around sunglasses with at least 99% UV absorption provide the best protection for the eyes and the skin area around the eyes. Look for sunglasses labeled as blocking UVA and UVB light. Labels that say “UV absorption up to 400 nm” or “Meets ANSI UV Requirements” mean the glasses block at least 99% of UV rays. If there is no label, don’t assume the sunglasses provide any protection.

Avoid tanning beds and sunlamps

Many people believe the UV rays of tanning beds are harmless. This is not true. Tanning lamps give out UVA and usually UVB rays as well, both of which can cause long-term skin damage and can contribute to skin cancer. Most skin doctors and health organizations recommend not using tanning beds and sun lamps.

If you want a tan, one option is using a sunless tanning lotion, which can provide the look without the danger. These lotions contain a substance called dihydroxyacetone (DHA). DHA interacts with proteins on the surface of the skin to give it a darker color. You do not have to go out in the sun for these to work. The color tends to wear off after a few days. These products can give skin a darker color (although in some people it may have a slight orange tinge), but if you use one you still need to use sunscreen and wear protective clothing when going outside. These tans do not protect against UV rays.

Some tanning salons offer DHA as a spray-on tan. A concern here is that DHA is approved for external use only and should not be inhaled or sprayed in or on the mouth, eyes, or nose. People who choose to get a DHA spray tan should make sure to protect these areas.

Protect children from the sun

Children need special attention, since they tend to spend more time outdoors and can burn more easily. Parents and other caregivers should protect children from excess sun exposure by using the steps above. It’s important, particularly in parts of the world where it is sunnier, to cover your children as fully as is reasonable. You should develop the habit of using sunscreen on exposed skin for yourself and your children whenever you go outdoors and may be exposed to large amounts of sunlight. Children need to be taught about the dangers of too much sun exposure as they become more independent.

Babies younger than 6 months should be kept out of direct sunlight and protected from the sun with hats and protective clothing. Sunscreen may be used on small areas of exposed skin only if adequate clothing and shade are not available.

A word about sun exposure and vitamin D

Doctors are learning that vitamin D has many health benefits. It may even help to lower the risk for some cancers. Vitamin D is made naturally by your skin when you are in the sun. How much vitamin D you make depends on many things, including how old you are, how dark your skin is, and how strong the sunlight is where you live.

At this time, doctors aren’t sure what the optimal level of vitamin D is. A lot of research is being done in this area. Whenever possible, it is better to get vitamin D from your diet or vitamin supplements rather than from sun exposure, because dietary sources and vitamin supplements do not increase risk for skin cancer, and are typically more reliable ways to get the amount you need.

For more information on how to protect yourself and your family from UV exposure, see our document Skin Cancer: Prevention and Early Detection.

Avoid a weakened immune system (when possible)

Having a weakened immune system increases the risk of getting MCC.

Some people need to take medicines to suppress their immune system. This includes people who have had organ transplants and some people with autoimmune diseases. People with cancer also sometimes need to take medicines that can lower their immune function. For these people, the benefit from taking these medicines will likely far outweigh the small overall increased risk of getting MCC.

Infection with HIV, the virus that causes AIDS, can weaken the immune system, which increases a person’s risk for MCC (and some other cancers). Avoiding known risk factors for HIV infection, such as intravenous (IV) drug use and having unprotected sex with many partners, can also lower your risk of getting MCC and many other types of cancer. (For more information, see our document HIV Infection, AIDS, and Cancer.)


Last Medical Review: 12/31/2013
Last Revised: 12/31/2013