What does MED measure?

MED, or Minimal Erythemal Dose, specifically measures the minimal amount of ultraviolet (UV) radiation exposure that causes redness or erythema in the skin. This is a critical concept in understanding skin's reactions to sunlight, as it helps determine an individual's sensitivity to sun exposure. The measure is often used in dermatology and sun safety to assess risk levels for sunburn and long-term skin damage.

In the context of the other choices, although skin moisture levels are important for overall skin health and sun protection factor pertains to sunscreen effectiveness, neither directly relate to the measure of how quickly skin reddens after sun exposure. Skin elasticity refers to the skin's ability to stretch and return to its original shape, which is unrelated to the concept of erythema resulting from UV light exposure. Thus, the focus of MED is explicitly on the skin's reaction to sunlight, aligning perfectly with the understanding of skin sensitivity and erythema.