The following are sources of moisture except:

Moisture is typically derived from various physiological processes and environmental factors. Urine and feces contribute to moisture due to their liquid and solid components, respectively, and they can harbor significant amounts of fluid. Wound drainage can include exudate, which is a fluid produced by the body in response to injury, further contributing to moisture levels. Perspiration, the body's process of sweating, explicitly serves to regulate temperature and maintain moisture on the skin's surface.

Barrier ointment, on the other hand, is specifically designed to create a protective layer on the skin. It is intended to lock in moisture while preventing external factors from eliciting moisture loss or skin irritation. As such, barrier ointments do not contribute to moisture but rather serve to protect and minimize moisture loss. This distinction highlights why it stands apart from the other options, which are inherent sources of moisture in various bodily functions or environmental exposure.