What increases in production in the skin as a response to exposure to ultraviolet light?

The skin increases the production of melanin in response to exposure to ultraviolet (UV) light. Melanin is a pigment that protects the skin by absorbing UV radiation. When skin cells detect UV exposure, they stimulate melanocytes, the cells responsible for producing melanin. This increased production of melanin leads to skin tanning, which serves as a natural defense mechanism against damage from UV rays. The presence of higher levels of melanin can help reduce the risk of skin damage, including sunburn and some types of skin cancer.

In contrast, while keratin is a vital protein for the structural integrity of the skin, its production is not directly linked to UV light exposure. Collagen, also important for skin structure and elasticity, is primarily affected by age and environmental factors rather than immediate UV exposure. Vitamin D production does increase with UV light exposure, but the focus of the question is on a pigment response rather than a vitamin synthesis response. Thus, melanin is the key player in the skin's response to UV radiation.