What is immediately affected in the skin after UV exposure?

Immediate erythema refers to the redness of the skin that occurs soon after ultraviolet (UV) exposure. When the skin is exposed to UV rays, it triggers an inflammatory response that causes blood vessels to dilate, leading to increased blood flow and redness in the affected area. This is the body's immediate reaction to the potential damage inflicted by UV radiation.

This response is important as it serves to alert the body to potential harm and to initiate protective measures. It typically occurs within hours of exposure and can vary in intensity depending on the duration and strength of the UV exposure, as well as the individual's skin type.

In the context of the other options, while melanin production does increase in response to UV exposure, this process is not immediate; it occurs as part of the body’s longer-term adaptation to UV radiation. Skin sloughing, or the shedding of skin cells, happens later as the skin renews itself, and the delayed tanning response refers to the gradual bronzing of the skin that develops after repeated UV exposure. Thus, the immediate effect of UV exposure is characterized by the occurrence of erythema.