What is the symptom of sudden reddening of the skin after prolonged exposure to the sun?

The symptom of sudden reddening of the skin after prolonged exposure to the sun is commonly associated with heat rash. This condition occurs when sweat ducts become blocked and sweat is trapped beneath the skin, leading to inflammation and redness. It tends to happen in situations of excessive sweating, especially in hot, humid environments, and commonly affects areas of the skin that are covered by clothing.

Heat stroke, heat exhaustion, and heat cramps are related to conditions caused by excessive heat but present distinct symptoms. Heat stroke is a severe and life-threatening condition characterized by a high body temperature, confusion, and altered mental state, while heat exhaustion includes heavy sweating, weakness, and nausea. Heat cramps primarily involve muscle spasms due to excessive loss of salt and water. These conditions do not primarily manifest as sudden reddening of the skin, which makes heat rash the correct answer in this context.