Though the sunburn you had in the summer may fade, your body doesn't forget that exposure to UV radiation. Changes in your skin's DNA due to UVA and UVB rays can cause serious, long-term skin damage.
One of the major downsides of UV radiation is that it advances the signs of aging. Premature wrinkling is common in people who have been exposed to the sun over long periods of time, as are age spots and uneven complexions. UV radiation can also cause cataracts and weaken the immune system [source: AAD: Exam].
But UV radiation is probably most notorious for causing various forms of skin cancer. Spending time in the sunlight affects melanocytes, the cells that produce melanin, a pigment that both gives skin its color and keeps it safe from UV rays. The rays cause melanocytes to produce more melanin. However, if the skin is overexposed to UV radiation, the melanocytes may change or experience abnormal growth, which causes cancer [source: Melanoma]. Melanoma is the most serious form of skin cancer, and it can spread quickly and appear anywhere on the body. Watch for pre-existing moles that become asymmetrical, vary in coloration or grow larger over time -- these are signs that you may have melanoma [source: AAD: Melanoma].
There are two nonmelanoma cancers that you should keep an eye out for as well. Basal cell carcinoma is the most prevalent form of nonmelanoma cancer. Although it is treatable and is not likely to spread (metastasize), it's easy to overlook, because it can appear in areas not typically exposed to the sun. Basal cell carcinoma usually shows up as a small, pearly bump and often requires a biopsy to confirm whether or not it's cancerous [source: WebMD]. Squamous cell carcinoma is another nonmelanoma form of cancer that, unlike basal cell carcinoma, can metastasize. Squamous cell carcinoma typically appears on sun-exposed parts of the body as scaly bumps, growths or lesions [source: AAD: Squamous].
Now that you know what types of cancers you should be aware of, read on to learn how artificial tanning can affect your melanocytes, and why a base tan is a bad idea.