Whether spending time out in the sun or spending time in a tanning booth, most people have had some contact to ultraviolet rays. The most common activity where this contact occurs is tanning. Tanning is the process of using the effects of ultraviolet light to increase pigmentation in the skin, resulting in a darker skin tone.

Ultraviolet rays can come in two main forms, UVA and UVB. According to the Skin Cancer Foundation, UVB rays are the more dangerous form of ultraviolet radiation. They are responsible for the formation of sunburns. UVA rays penetrate deeper into the skin and influence the deeper skin cells, allowing the rays to influence the production of melanin.

Once ultraviolet rays penetrate the skin, the work directly on cells called melanocytes. Melanocytes are responsible for producing melanin, the substance in your body that give the skin its coloring. The ultraviolet rays work as a catalyst for the increased production of melanin. The more time spent exposed to ultraviolet rays, the more melanin that will be released. The greater amount of melanin released, the darker the tan will become.

Without sunblock, UVA and UVB rays can increase your risk of skin cancer. Regardless of whether physical manifestation of skin damage occurs (such as a sunburn) even unnoticeable damage can create the right conditions for skin cancer development. When the body tries to fix cells that have been damaged by ultraviolet radiation, the DNA of the cell can sometimes become altered. This alteration can cause the skin cell to grow irregularly, and develop into a cancerous cell. According to the American Cancer Society, you should wear at least SPF 15 protection sunblock when spending time in the sun. SPF 15 will block an estimated 93 percent of UV rays, with SPF 30 and SPF 50 blocking 97 percent and 98 percent, respectively.