What Causes Sunspots on Skin?

Cynthia Bailey, MD|September 8, 2014

sunspot on skin of Woman applying beauty creamSunspots on skin, called solar lentigines, are due to sun exposure. They are flat brown spots that show up on the parts of your skin that have been exposed to the sun. Once you start getting sunspot on skin, expect them to darken and increase in number with every UV ray that hits your skin.

Any UV ray from the sun will darken your sunspots. Yes, that means that even the sun that comes through windows, that bounces off cement or water, or that passes through clouds will worsen your sunspots.

What about tanning beds - can you outwit the process by tanning using unnatural UV light? No, tanning-bed UV rays will cause sunspot on skin too. In fact, tanning-bed “freckles” as they are called, are often more numerous on the skin than natural-light sunspot. They also, in my opinion, have a really unnatural look, which means that when I do a skin exam I can usually tell if my patient has had tanning bed exposure.

Think of the cause and effect this way,

any UV Ray exposure = sunspots!

Almost everyone will eventually get sunspot on skin from sun exposure. Some people start getting them earlier in life. These are usually people with really fair skin. If your skin is prone to developing sunspots they can start showing up as early as your 20's, though most people start really noticing them in their 30's and 40's.   sunspot on skin - solar lentigines Solar lentigines, aka sunspots, on the side of the face Your first sunspots often show up on the sides of your face, the sides of your neck, the v of your chest, and the back of your hands. These are the areas of your skin that get the most lifetime sun exposure. If you are a man whose scalp hair is thinning, sunspots will start dotting the top of your scalp too. Eventually all of the parts of your skin that are exposed to the sun will develop sunspots. The shaded areas have fewer or none. To see this, find someone with sunspots on their arms. Look at the outer side of the arm and compare it to the underside. There are usually many more sunspots - both small and large - on the outer side of the arm than on the sun-protected underside. Sunspots on skin are harmless. They don’t turn into skin cancer BUT, skin cancer can mimic a sunspot. All of the common skin cancer types can start as a flat brown patch. Because sunspots often have irregular boarders and variable shades of brown it may be hard to tell by looking if a brown spot is worrisome for skin cancer.  

Said another way, sunspots on skin can have the ABCDE signs of melanoma, meaning that you may need a skin exam by a dermatologist in order to tell the difference.

Also, the presence of a lot of sunspots indicate that you have had more sun exposure than your skin can handle, which means that you are at increased risk for skin cancer in the areas with the spots. It’s safest to have an annual skin exam done by a dermatologist if your skin has a number of sunspots. In addition, your skin will have a unique "style" or pattern to its sunspots and your dermatologist can teach you how to better tell the difference between your sunspots, your other age spots and skin cancer. Once you know this information, you can then do your own monthly skin exams with more confidence. What exactly are sunspots on the skin? Sunspots on skin are a focal increase of skin pigment called melanin; because of UV exposure, the pigment-making cells, called melanocytes, produced excess pigment in just one spot instead of uniformly across your skin surface. The important point is that there is no increase in the number of the melanocyte cells, just in the pigment that they produced. Moles and melanoma, on the other hand, have an increase in number of the actual melanocyte cells. In the case of moles, these melanocytes are not cancerous. In the case of melanoma, the melanocytes are cancerous. The cancerous cells of melanoma can spread all over the body and kill. When you are looking at brown spots on your skin it is not always easy to tell the difference between a sunspot, a mole, and a melanoma with the human eye. This is why doctors sometimes have to perform biopsies of brown skin spots to make an exact diagnosis. A biopsy is a procedure where either the entire brown spot or part of it is cut out and examined with a microscope. It allows the doctor to clearly see what’s going on under the skin to determine if the brown spot is made up of only skin pigment or if there is also an increase in the pigment producing cells called melanocytes. Assuming that all the unwanted brown spots on your skin are, in fact, just sunspots, how can you get rid of them? I’ll talk about that in the next post.

What are your questions and concerns about sunspots on skin? 

Let us know by commenting below.

  Don't miss the other posts in this series: Post 2. How Can You Get Rid of Skin Sun Spots? Photo attribution: Thanks and gratitude to © Laura Doss/Corbis

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