How Skin Moles Work

Portrait on young woman with facial mole.
In centuries past, people put fake beauty marks on their faces. See more pictures of skin problems.
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Skin moles have been portrayed as ugly blemishes marring the faces of villains and witches. They've also been seen as sophisticated marks of beauty, gracing the faces of the world's most renowned celebrities and supermodels.

Moles are an incredibly common occurrence; nearly everyone has at least a few. Most prevalent in fair-skinned people, skin moles are generally harmless skin growths that result from a high concentration of natural skin pigment. In most cases, moles go through their normal life cycle without ever causing a problem -- they're merely a normal part of a person's skin.


While most are not, skin moles can also be an important indicator of skin cancer. It's important to learn about the different types of skin moles in order to evaluate whether one may be cancerous. Certain symptoms may indicate the development of an atypical mole, which a doctor should check. You'll learn more about the mole-cancer connection in a couple pages, but for the majority of people, skin moles are just a part of everyday life.

This article also explores the types of skin moles, their causes and possible medical and cosmetic treatments. Read on to learn more about the types of skin moles and signs for which one should watch when examining the skin.


Types of Skin Moles

Skin moles, also known as nevi, are a common type of skin growth that can occur anywhere on the body. Most people have moles, and many people have between 10 and 40 moles by adulthood [source: WebMD]. Skin moles usually appear brown or black in color, and they can be any shape or size. Each mole has a different growth pattern, so a mole may change over the course of a person's life. A shift in a mole's appearance isn't, in itself, a cause for concern.

Generally, a mole begins as a flat, tan spot like a freckle on the skin. As a person ages, the mole can become more raised and its color may change, or the mole may disappear or fall off. These are natural changes in the life cycle of a mole, which may last as long as 50 years [source: American Academy of Dermatology].


Two types of moles are more likely to present problems later in life: congenital nevi and dysplastic nevi. Congenital nevi are moles that are present at birth. They occur in about one in 100 people [source: WebMD]. These moles may be more likely to develop into melanoma than moles that occur after birth, so it's important to watch for significant changes.

Dysplastic nevi, or atypical moles, are larger-than-average moles that have an irregular shape. They have uneven coloring, usually with dark brown centers and lighter, jagged edges. Dysplastic nevi may also have a reddish border or small black dots around their edge. People with dysplastic nevi often have 100 or more moles. These moles tend to run in families and can also pose a risk of melanoma [source: American Academy of Dermatology].

Being able to recognize the different types of moles is important for conducting self-examination, which can help individuals identify moles that may develop problems later.

So what causes moles, anyway?


Causes of Skin Moles

Moles are common skin growths that result from a natural process in the skin. Melanin is the natural pigment that gives skin, hair and the irises of the eyes their color. In the skin, melanin is produced in cells called melanocytes located in the two upper layers of the skin. Melanocytes tend to be spread evenly throughout the skin, giving the skin its natural color. When exposed to the sun, melanocytes produce more melanin, darkening the skin with a suntan [source: National Cancer Institute]. When melanocytes don't distribute evenly and instead grow in clusters, moles form [source: Mayo Clinic].

Moles can form anywhere on the body, but they tend to grow more often on areas exposed frequently to the sun, such as the hands, arms, chest, neck and face [source: Cleveland Clinic]. Normally, moles form in the first 20 years of a person's life, though some may grow later. Some moles, especially dysplastic ones, are thought to be influenced by genetics.


Most nevi are a common occurrence that shouldn't cause a person concern. As moles evolve over a person's lifetime, however, they may present problems. Read on to find out how.

Skin Moles and Cancer

A melanoma begins to develop when melanocytes, the same cells that cause moles, begin dividing without control or predictable order. These abnormal cells then invade and destroy the cells around them, causing malignant tissue to grow on the surface of the skin. A melanoma can begin as an existing mole, or it can develop as a new skin growth [source: National Cancer Institute].

While most moles are completely harmless, moles are a risk factor for melanoma. Those with many ordinary moles (more than 50) and those with dysplastic nevi are more susceptible to melanoma. Other risk factors include a family history of melanoma, exposure to UV radiation, a history of severe or blistering sunburns, freckles and pale skin [source: National Cancer Institute].


Doctors advise individuals concerned about melanoma to follow the ABCDE rule. This rule indicates that if a person has a mole that falls into any of the following categories, he or she should consult a dermatologist:

  • A is for "asymmetry," which refers to a mole that doesn't appear the same on each side
  • B is for "border," referring to a mole with a blurry or jagged edge
  • C is for "color," meaning moles that change color, either darkening or lightening, or that have the appearance of multiple colors
  • D is for "diameter," referring to a mole that is larger than .25 inches (.64 cm) in diameter, or about the size of a pencil eraser
  • E is for "elevation," indicating a mole that is raised above the skin and has a rough surface

[source: American Academy of Family Physicians]

In addition to the ABCDE symptoms described above, any translucent, pearl-shaped growth or mole that has begun to grow, bleed or itch requires consultation with a dermatologist [source: American Academy of Dermatology].

The most important thing to remember about melanoma is that it can be cured with minimal surgery when caught early [source: National Cancer Institute]. For this reason, individuals should watch for any signs of abnormality in moles.

Read on to learn more about the processes of mole removal.


Skin Mole Removal

Your doctor may recommend that an atypical mole be removed for health reasons, or you may decide to have a mole removed for cosmetic reasons. Either way, mole removal is a relatively low-risk procedure. The surgery itself may result in light scarring, depending on the type of mole that is removed, but your doctor can give you a better idea of how the area will look after surgery depending on the type of method used.

The two most widely used forms of mole removal are excision followed by stitches and excision with cauterization [source: eMedicine]. The first method involves cutting off the mole and resealing the wound with stitches. In the second method, a tool burns away the mole, cauterizing, or sealing, the wound as the mole is removed. Both methods are outpatient procedures during which the patient undergoes anesthesia, resulting in minimal pain.


Doctors have also tried laser treatment to remove moles, but this method doesn't penetrate as deeply as the other methods, which can be problematic for moles with deeper roots beneath the skin [source eMedicine].

Dermatologists may have many reasons for removing a mole with surgical excision. If a mole has become irritating to the skin or shows warning signs of melanoma, a doctor may remove the mole to prevent it from becoming cancerous. Individuals may also choose to remove moles for cosmetic reasons, to improve the appearance of the skin or to remove a mole that, though not medically worrisome, has become larger over time [source American Academy of Dermatology].

Individuals concerned about mole growth for medical or cosmetic reasons should consult with a dermatologist to determine whether to remove it and to determine the best method of removal.

Want more information on moles and other skin conditions? Follow the links on the next page.


Lots More Information

Related HowStuffWorks Articles

  • American Academy of Dermatology. "Atypical Moles: How to Recognize." SkinCancerNet. 2009. (Accessed 8/9/09)
  • American Academy of Dermatology. "Moles." 2007. (Accessed 8/8/09)
  • American Academy of Family Physicians. "Melanoma: A Kind of Skin Cancer." May 2006. (Accessed 8/10/09)
  • Bakalar, Nicholas. "Having Moles May Mean Younger Skin Cells." The New York Times. July 24, 2007. (Accessed 8/10/09) http://query.nytimes.comgst/fullpage.html?res=9C06E6D81138F937A15754C0A9619C8B63&scp=2&sq=moles&st=nyt
  • Cleveland Clinic. "Moles, Freckles, Skin Tags, Benign Lentigines, and Seborrheic Keratoses." 2009. (Accessed 8/10/09)
  • eMedicineHealth. "Mole Removal." July 14, 2009. (Accessed 8/10/09)
  • Mayo Clinic Staff. "Moles: Causes." February 19, 2008. (Accessed 8/9/09)
  • National Cancer Institute. "Melanoma." September 16, 2002. (Accessed 8/10/09)
  • National Cancer Institute. "Moles." September 16, 2002. (Accessed 8/9/09)
  • WebMD. "Skin Conditions: Moles, Freckles and Skin Tags." March 1, 2007. (Accessed 8/7/09)