Horses sweat through pores all over their bodies, similarly to humans. Unlike humans, horse sweat contains the protein latherin, which helps spread the sweat over the horse's body for faster evaporation. This protein gives horse sweat a soapy feeling similar to laundry detergent.
While working or exercising, a horse loses 4 gallons of water an hour. When horses sweat, they also lose sodium and chloride ions known as electrolytes. The loss of electrolytes occasionally prevents horses from feeling the urge to drink. This leads to dehydration. Caution should be taken when working or exercising a horse during times of high heat or humidity.