Two of the main problems with preventing and treating cancer is that it is not always clear what the external environmental condition is that causes the cancer and being able to detect the tumor growth before it becomes hard to treat. In the case of skin cancer it is generally agreed that exposure to ultraviolet radiation (UV rays) is the environmental condition. And in most cases, the cancer is on the surface of the skin so can be detected quickly. The most common form of UV rays that people are exposed to are in sunlight.

However, some people can spend more time in the sun than others without developing skin cancer. Their skin is not as sensitive to the sun. This is because they have more melanin in the body. Amongst many other functions, melanin makes the skin go brown when exposed to the Sun. This is the body's natural method of protecting skin cells. This is the tan that many people like to develop as they see it as an indication of health and vitality.

People who have less melanin will have paler skin. This often means that the skin will not brown but go red in the sun. It will also burn if they spend too much time in the sun or don't protect their skin. Sunburn is obviously painful but it also indicates that the skin has been exposed to too much UV rays. It is the best way to develop cancerous growths on the skin. People with fair or red hair or light colored eyes are also sensitive to the sun.

Another factor that can increase the chances of developing skin cancer is any family history of the disease.

The effects of skin cancer vary depending on the type of carcinoma. Basal cell carcinoma is the most common type of skin cancer. It is normally found on areas of the body directly exposed to the sun. It is generally a mark or spot on the skin that could be brown or red. In most cases it will not spread from the original location.

Squamous cell carcinoma is also found on parts of the body that come into contact with sunlight. This form of skin cancer is more likely to spread than basal cell carcinoma but it generally only spreads to the surrounding skin cells. Often the blemish or mark will look brown or red. This mark will get bigger over time as more cells become cancerous. It can also become scaly and develop scabs.

Melanoma is the rarest but most serious form of skin cancer that can develop. Unlike the other two, it can occur anywhere on the body, including areas that may not get much exposure to sunlight. For instance, the feet may develop a melanoma. It normally looks like a brown or red mark but as it develops it may become a lump under the skin. It may also look like a mole on the surface of the skin that changes color and starts to get bigger.

Of the three forms of skin cancer, melanoma is most likely to be malignant. This means it can grow at an uncontrollable rate and spread to other parts of the body. When this occurs it can become invasive, in that it will grow through other tissues or organs destroying them in the process. Even if it does not destroy organs, the melanoma can become so large that it prevents the organs from functioning properly.

Depending on where the cancer spreads or metastasizes this can be extremely hard to treat and potentially life threatening.

The best way to guard against skin cancer is to limit your exposure to sunlight and protect your skin when in the sun. Also monitor any unusual skin blemishes or lesions or unusual lumps. Get your skin checked out from time to time by a skin specialist. Avoid other things that can expose you to UV rays.