A risk factor is anything that may increase your chance of having a disease. Risk factors for a certain type of cancer might include smoking, diet, family history, or many other things. The exact cause of someone's cancer may not be known. But certain risk factors may make it more likely for a person to have cancer.

Things you should know about risk factors for cancer:

• Risk factors may increase a person's risk for developing the disease, but they don't necessarily cause the disease.
• Some people with one or more risk factors never develop cancer, while other people can develop cancer and have no risk factors.
• Some risk factors are very well known. There is ongoing research about risk factors for many types of cancer.

Some risk factors, such as family history, may not be in your control. But other factors might be things you can change. Knowing the risk factors can help you make choices that might lower your risk. For example, sun exposure is a risk factor for melanoma, so you can protect yourself from the sun to help lower your risk.

The most common risk factors for melanoma include:

• Age. Melanoma is more common in older people, but it is still one of the more common cancers in people younger than age 30, especially those who are biologically female.
• Gender. Male risk for melanoma is higher overall, but female risk is higher before age 50.
• Sun exposure. Sunlight, the main source of ultraviolet (UV) light rays, is a major risk factor for melanomas (and other skin cancers). Some research suggests that having many sunburns, especially in childhood, might increase the risk of getting melanoma.
• Artificial tanning. Tanning beds emit UV rays. The use of tanning beds and sunlamps has been linked to an increased risk of melanoma.
• Moles. While most moles are harmless, people who have many moles or abnormal moles (dysplastic nevi) are at increased risk for melanoma.
• Fair skin, light hair. People with light-colored skin are many times more likely to develop melanoma than those with darker skin. People with very pale skin, those who freckle easily, those with red or blond hair, or those with blue or green eyes are at higher risk.
• Family history. People whose parents or siblings have had melanoma are at higher risk of melanoma. In some families, people share specific gene changes that increase their risk. For example, some families share changes in a gene known as CDKN2A, which increases their risk. Still, known gene changes account for only a small portion of melanomas.
• Certain inherited conditions. People with certain rare, inherited conditions, such as xeroderma pigmentosum, are at increased risk for melanoma.
• Personal history of skin cancer. People who have had melanoma or another type of skin cancer in the past are more likely to develop melanoma again.
• Weak immune system. People who have a weak immune system, such as people who have had an organ transplant or those infected with the HIV virus, are at higher risk for melanoma.

Talk with your doctor about your risk factors for melanoma. You may be advised to have frequent skin exams at your doctor's office along with doing monthly skin exams on yourself at home. There are also things you can do that might lower your risk for melanoma, such as protecting yourself from the sun and not using tanning beds. Talk with your doctor about the best ways to reduce your risks.