Dogs cannot drink pure milk. Because milk contains lactose, and dogs’ digestive systems are not suitable for digesting lactose like humans, drinking pure milk can cause digestive problems such as diarrhea and abdominal pain in dogs. At the same time, the fat content in milk is high, and long-term consumption can lead to health problems such as obesity and cardiovascular disease in dogs.

Pure milk also has a high protein content. Long-term drinking will increase the burden on the dog's kidneys and may cause kidney disease; in addition , the bacterial content in milk is high, which can easily cause infectious diseases in dogs.