Which of the following is a sign of overexposure to UV light?

Itchy or blistered skin is a clear indicator of overexposure to UV light. When the skin is subjected to excessive UV radiation, it can lead to sunburn, which manifests as red, swollen, and painful skin. In more severe cases, this overexposure can cause blistering and intense itching as the skin reacts defensively to the damage caused by UV rays. This reaction reflects the skin's inflammatory response, which is a protective mechanism in reaction to injury or excessive ultraviolet exposure.

The other options, while associated with tanning and skin health, do not signal overexposure. Enhanced tanning and increased melanin production are normal responses to controlled sun exposure and are not indicators of overexposure but rather a sign of the skin attempting to protect itself. Greater skin elasticity is generally viewed as a positive health indicator and does not correlate with the damaging effects of UV overexposure. Thus, the presence of itchy or blistered skin directly signals that the skin has been harmed by too much UV light.