Ultraviolet radiation–induced erythema is especially intense after which time interval?

• A. 1-2 hours
• B. 3-4 hours
• C. 5-6 hours
• D. 7-8 hours

Answer: (B)

Ultraviolet exposure triggers an inflammatory response in the skin, with mediators like histamine and prostaglandins causing vasodilation and redness. This takes a short latent period, and the intensity of the erythema usually reaches its maximum a few hours after exposure. The most intense erythema is typically seen around three to four hours post-exposure, reflecting the time needed for the inflammatory cascade to amplify and for the visible redness to become pronounced. By seven to eight hours, the redness may begin to level off as initial repair processes start. So, the three-to-four-hour window best captures when UV-induced erythema is strongest.