How do moles form in the skin?

I've always wondered specifically, how do moles form in people's skin? I know some of it is hereditary and related to the skin cells. Also I was wondering if there is any way of either preventing moles from forming or getting rid of moles without the use of surgery?

From WebMD:
"Moles occur when cells in the skin grow in a cluster instead of being spread throughout the skin. These cells are called melanocytes, and they make the pigment that gives skin its natural color. Moles may darken after exposure to the sun, during the teen years, and during pregnancy."

R. Cooper, Librarian
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aging is one cause of developing a mole..

Moles, while cute, are considered to be an agricultural pest in some countries, while in others, such as Germany, they are a protected species but may be killed if a permit is received. Problems cited as caused by moles include contamination of silage with soil particles making it unpalatable to animals, the covering of pasture with fresh soil reducing its size and yield, damage to agricultural machinery by the exposure of stones, damage to young plants through disturbance of the soil, weed invasion of pasture through exposure of fresh tilled soil, and damage to drainage systems and watercourses. Other species such as weasels and voles may use mole tunnels to gain access to enclosed areas or plant roots.

Moles that burrow in the lawns of humans can disturb the earth, raising molehills and causing enough aesthetic problems, and killing enough of the lawn, to be considered as pests. They do however benefit the soil by aerating and tilling it, adding to its fertility. Contrary to popular belief, moles don't eat plant roots.

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Oh, sorry, wrong type of mole! Moles have two major causes. Sunlight and Genes. Some scientists suspect that overexposure to ultraviolet light, including excessive sunlight, may play a role in the formation of acquired moles. However, more research is needed in this area.

Genes can also have an influence on a person鈥檚 moles. Dysplastic nevi or atypical mole syndrome is a hereditary condition which causes the person to have a large quantity of moles (often 100 or more) with some larger than normal or atypical. This often leads to a higher risk of melanoma, a serious skin cancer. A slight majority of melanomas do not form in an existing mole, but rather create a new growth on the skin. Nevertheless, those with more dysplastic nevi are at a higher risk of this type of melanoma occurrence. Such persons need to be checked regularly for any changes in their moles and to note any new ones.