Coffee with pure milk is generally not harmful, if long-term excessive consumption may cause insomnia, gastrointestinal discomfort and so on. Coffee is a kind of beverage, coffee contains niacin, potassium, crude fiber, caffeine, alkaloids and other substances. Pure milk is rich in fat, various proteins, vitamins, minerals, vitamin B, calcium and other ingredients. Each one hundred milliliters of milk contains 54 calories, of which 3.4 grams of carbohydrates, 3 grams of protein, 3.2 grams of fat and 104 milligrams of calcium. Moderate consumption of coffee with pure milk is generally not harmful to the human body. However, coffee with pure milk has some contraindications, such as sleep disorders, gastric ulcers, lactose intolerant people, etc., due to the caffeine in coffee can cause nerve excitation, causing difficulty in falling asleep; coffee is easy to promote the increase in gastric acid, excessive coffee can aggravate the symptoms of gastric ulcers; lactose intolerant people drink pure milk can cause bloating, diarrhea and other gastrointestinal symptoms. Milk allergy should not drink coffee with pure milk.