What distinguishes heat stress from heat illness?

Heat stress is characterized as the buildup of heat in the body during work or physical activity, particularly in hot environments. This accumulation of heat occurs when the body is unable to dissipate heat effectively through processes like sweating and increased blood flow to the skin. As work continues, especially in warm conditions, the body can experience an imbalance where the heat produced theoretically exceeds the heat being lost, leading to physiological changes.

The other options do not accurately capture the distinct relationship between heat stress and heat illness. For instance, heat stress can occur even in highly hydrated individuals if environmental conditions are excessively hot. Similarly, heat illness encompasses a range of health issues resulting from prolonged exposure to heat, which might involve dehydration but is not solely limited to it. Thus, understanding heat stress primarily as a build-up of body heat is essential for identifying when preventive measures are required to avoid heat-related health issues.