One of the appendages of the skin is the cuteneous gland. it has two categories which are the sudoriferous(sweat) gland and sebaceous(oil) gland. the causes of sweat under arms is because of its sweat gland.
'Sweating' A horse refers mainly to placing a type of neck cover on the horse after applying a 'sweating gel/lotion' and letting the heat made by the trapped liquid to cause the horse to sweat of the 'excess' neck weight causing the neck to look thinner and longer.
The presence of water vapor due to faulty seals is what causes double pane windows to sweat. Double window panes sweat because sunlight causes the gas inside to expand which stresses the seal and allows water vapor inside.
Sweat is what causes body odor. Sweat has the same chemical makeup as your urine at that time. So it depends on what you have ingested. Body odor is actually the drying/fermentation of your sweat. Which is why it can smell so strong. It's been concentrated.