If you've noticed new moles appear on your legs over the years, you may have assumed it was because of the sun. After all, our limbs can get a lot of UV exposure, especially during the warmer months. But even though sunshine is a factor, new research shows genetics also play a crucial role — especially when it comes your legs.
An August 2019 study published in Pigment Cell & Melanoma Research found that genes have a much greater influence than previously thought on both the number of moles you have, as well as where those moles appear on your body. Researchers analyzed a group of 3,200 healthy twins (who were predominantly female) and counted the moles on their heads, necks, backs, abdomens, chests, upper limbs, and lower limbs.
Results showed that in women, a large number of moles on the lower limbs were unlikely due to sun exposure alone. Instead, they found it was because of a sex-specific genetic makeup. By studying female twins, researchers found the highest genetic effect in moles on the women's legs — a whopping 69 percent. Interestingly enough, the moles found on participants' backs and abdomens had the lowest genetic effect at just 26 percent. So in other words, a mole on your back may be there from sunbathing, but a mole on your thigh just might be there because you inherited it.
"We've known for some time that moles are a major risk factor for melanoma skin cancer. With this research we now know that not only the number but also the location of moles on the body is in large part due to genetics," said lead researcher Alessia Visconti, PhD, in a press release. "Our results add to previous evidence that indicates greater sun exposure alone is unlikely to be the reason why women have more moles on their legs."
Dr. Visconti added: "While sun exposure does contribute to mole count and skin cancer risk, policymakers, campaigners, and health researchers will need to take the sex-specific genetic element into account when developing strategies to prevent and treat skin cancer."
It's comforting to know that having moles on your legs isn't necessarily indicative that you've gotten an unhealthy amount of UV rays. However, it's important to remember that even though the moles on your legs are more likely genetic, there's not really a way to prove that at home.
So as always, remain cautious and check with your dermatologist if you spot anything unusual or worrisome on your skin. And no matter how many or how few moles you have, it's important to remember to keep wearing that sunscreen — as summer scorches on and throughout the year.