What is the condition characterized by the absence of sweat secretion?

Anhidrosis is the condition defined by an absence of sweat secretion, which means the body is unable to produce sweat effectively. This can occur in various circumstances, such as due to certain medical conditions, genetic factors, or damage to sweat glands. The lack of sweating can lead to overheating and heat-related illnesses because sweating is a crucial mechanism for regulating body temperature.

In contrast, hyperhidrosis involves excessive sweating, where the body produces more sweat than necessary. Dermatitis refers to inflammation of the skin and is typically characterized by a variety of symptoms such as redness, itching, and flaking, but does not primarily relate to sweat production. Acanthosis nigricans is a skin condition marked by areas of dark, velvety patches, usually in body folds, and is linked to insulin resistance rather than issues with sweating. Therefore, anhidrosis is the correct choice as it directly defines the condition of sweat absence.