factors that cause skin cancer

Fair complexion: Having light skin, skin that freckles or burns easily and blue eyes increases your risk of skin cancer.
Moles: Irregularly shaped or colored moles and having lots of moles may increase your risk of melanoma.

Chemical exposure: Exposure to arsenic, a heavy metal used in making some insecticides, and found in some water supply, increases the risk of developing non-melanoma skin cancer. Occupational exposure to industrial tar, coal, paraffin and certain types of oil also may increase the non-melanoma skin cancer risk.

Radiation exposure: Radiation therapy may increase the risk of a non-melanoma skin cancer.
Long-term or severe skin inflammation or injury: In rare cases, non-melanoma skin cancers grow in scars from severe burns, on areas of skin over severe bone infections, and on skin damaged by certain severe inflammatory skin diseases.
Psoriasis treatment: Patients treated with the drug psoralen and ultraviolet light (PUVA) may have an elevated risk of squamous cell carcinoma.

Actinic keratosis: These thick scaly patches of skin can sometimes develop into cancer.
Xeroderma pigmentosum: This very rare hereditary disease makes it difficult for the skin to repair DNA damage from UV light. Xeroderma pigmentosum patients typically suffer many skin cancers, which may begin in childhood.

Basal cell nevus syndrome: People born with this rare condition develop multiple basal cell carcinomas and other health problems.
Reduced immunity: People whose immune system is diminished because of HIV infection, drugs that prevent rejection of donor organs or chemotherapy are at increased risk for non-melanoma skin cancer. New immune drugs used to treat skin disease may affect the body's immune system and increase the risk of cancer, especially lymphomas.