Why is skin considered an excretory organ

"Skin is considered an excretory organ because you sweat through your skin. It is part of the excretory system, that helps regulate heat and the concentration of salt in the body. The salt helps evaporate the water, cooling off the skin. Sweat is excreted through sweat glands. There are two types of sweat glands: eccrine sweat glands and apocrine sweat glands."