Causes of Moles

People may wish to know what causes moles, since they can pose both medical and cosmetic problems. Several different factors influence the number and type of moles a person might develop, some of which are out of a person's control. Knowing what factors are within one's control can help a person to take action to minimize the number of moles that develop, which may be a desirable outcome, since moles that develop past young adulthood can be particularly prone to developing into cancerous growths. Researching and consulting a doctor about one's moles can also be beneficial, since a doctor can give patients information with the patient's family and medical history in mind.

Moles occur when pigment skin cells called melanocytes cluster together. Melanocytes are usually evenly dispersed throughout the skin. The gene that influences mole formation and a person's predisposition to developing melanoma has been identified, but the actual process of mole development is still unknown.

Genetic Factors

Heredity is the primary factor that influences a person's tendency to develop moles. Immediate relatives such as parents and siblings are the best indicator of what a person's predisposition to forming moles is going to be. Mole-related conditions such as atypical mole syndrome and melanoma often run in families. Identical twins have similar numbers and types of moles, which is the most compelling demonstration of the significance of genetics in developing moles. Most of the moles a person develops throughout their lifetime are probably genetically determined. Since a person cannot change their genetics, most moles that develop are outside their control.

Epigenetic Factors

In addition to the moles themselves being genetically determined, some inherited traits leave a person more susceptible to epigenetic causes of moles. Epigenetic causes are factors other than genetic causes. For instance, people with fair complexions or light-colored eyes or hair, heritable traits, are more easily burned in sunlight. As a contrast, people with darker complexions are not as susceptible to sunburn or to develop moles. Since a person's sensitivity to sunburn and sun exposure is associated with acquired moles, moles that form after young adulthood or that form as a result of epigenetic factors, this is another genetic factor that influences mole formation.

Moles and Hormones

Hormonal changes often trigger new mole growth or changes in the appearance of existing moles. Moles appear and change mostly during long periods of hormonal change and activity. The exact role of hormones in encouraging new mole growth and existing mole changes is not clear, but experts have noticed a correlation between periods of hormonal change and mole growth. Puberty is the first of such periods of hormonal change people tend to experience. Many of the moles a person forms appear during puberty and young adulthood. Frequent mole growth tends to slow down around the time a person reaches twenty years of age, although new moles tend to continue to appear at a slower rate for years afterward.

Women tend to develop more new moles throughout their lives than men do, since women may have more periods of prolonged hormonal changes during their lives. Pregnancy and menopause are two such periods men do not experience. Women may see new moles form and existing moles darken and increase in size and elevation during pregnancy. Pregnancy does not affect the risk of developing melanoma, so changes in moles during pregnancy are usually a benign effect of hormonal activity that occurs during pregnancy. However, melanoma can develop at the same time as pregnancy, so if the mole's texture or border changes or becomes irregular, or if the mole becomes dry and itchy, a visit to a dermatologist may be needed to assess the mole's risk of forming a melanoma, particularly if the pregnant woman has a family or personal history of melanoma.

Moles tend to change in similar ways during menopause. Some birth control pills also cause similar effects on moles as pregnancy and menopause do; people with a family or personal history of melanoma may wish to change their birth control pill or contraceptive method if moles are a problem. Other than birth control pills, hormonal causes of moles are, like genetic causes, not under the control of the person.

Moles and UV Radiation

Exposure to sunlight and non-natural sources of ultraviolet radiation is the most prominent epigenetic cause of moles. People who are frequently exposed to UV radiation, including in tanning beds, often see new mole growth or changes in existing moles. This is probably because exposure to sunlight, particularly when the sun exposure leads to burning, causes an increase in melanin production, which leads to tanning.

Melanin is the pigment produced by melanocytes, the cells that cluster and cause moles to form. Melanin is a protein that functions to protect the skin against the damaging effects of UV radiation. Increasing the activity of melanocytes leads to increased numbers of melanocytes, which make them more prone to cluster and form new moles. It can also excite the melanocytes that form existing moles to produce more melanin in the moles or to reproduce, which can lead to darkening and elevating.

When cells reproduce, as melanocytes do under increased exposure to sunlight or other sources of UV radiation, genetic mutations can occur. This may lead to unchecked cellular growth. Malignant tumors are masses of cells that undergo uncontrolled growth. When a person continues to expose themselves to UV radiation, they are likely to see an increase in the number of moles on their body and expose themselves to a greater risk of developing skin cancer.

Most factors that contribute to mole growth and darkening are largely out of the person's control. Whether or not new moles form or become cancerous seems to be mostly influenced by genetics and hormonal activity, which are outside the reaches of outside intervention. However, the effects of exposure to UV radiation on the skin and on moles are not insignificant, and minimizing sun exposure and refraining from using tanning beds can prevent new moles from forming and is the best prevention against melanoma and other skin cancers.