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How does long-term sun exposure contribute to basal cell carcinoma and squamous cell carcinoma?

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skin rash caused by Lyme disease — skin disease Visible alterations in the texture of the skin, such as rashes and hives, can be indicative of serious disease. For example, one of the first signs of Lyme disease is a circular rash in a bull's-eye pattern on the skin.

Long-term exposure to ultraviolet (UV) radiation from the sun is a primary cause of basal cell carcinoma and squamous cell carcinoma. These cancers, which originate in the epidermis, are largely the result of cumulative DNA damage within skin cells.123

The carcinogenic process is driven by the formation of pyrimidine dimers—structural changes that occur between adjacent nucleotide bases (cytosine and thymine) in DNA when exposed to UV light. If these mutations occur in growth-regulatory genes and are not successfully repaired by the body’s cellular mechanisms, they can initiate and promote the uncontrolled cell growth characteristic of carcinomas.145

The risk of developing these cancers is influenced by factors such as the intensity of UV exposure, the individual's skin pigmentation, and the amount of protective melanin present. Because UV radiation acts as a mutagen, prolonged or repeated exposure significantly increases the likelihood of developing these malignancies over time. Protecting the skin with sunscreen and clothing is essential for reducing this risk.1523