There is no harm. Most coffee and coffee drinks are consumed with milk and various dairy products. Milk can neutralize part of the bitter taste of coffee, making the coffee smooth and easy to drink. Drinking milk at the same time can also prevent the loss of calcium caused by drinking coffee. Coffee contains caffeine, which will excite the sympathetic nerves after entering the body, thereby eliminating drowsiness, improving blood circulation, and the body will feel warmer and less fatigued, so it has a "refreshing" effect. However, the stimulation and excitement of the sympathetic nerves will have a negative effect on appetite, that is, the appetite will be reduced, so drinking coffee before a meal will make you not want to eat. In addition, because the stomach is stimulated, gastric juice secretion increases, stimulating an empty stomach, which is detrimental to patients with gastric ulcers and other diseases. This can be said to be a negative effect of coffee. But drinking it after a meal will help digestion because gastric juice secretion will increase. So drinking it after a meal is absolutely fine. In addition, some people think that adding a little milk to drink can alleviate its irritating effect. However, how much can a small amount of milk neutralize caffeine? Unless it is half milk and half coffee, mixed into coffee milk or milk coffee, it may have some effect. For example, if you drink coffee and milk for breakfast, since there is more milk than coffee, even if you drink it on an empty stomach, it still has the effect of soothing gastric juices. The best thing is to drink it after eating, then it will be beneficial but not harmful. One benefit is preventing allergy attacks. Asthma or allergic rhinitis is caused by the excitement of the parasympathetic nerves in the allergic system. If it can promote the excitement of the sympathetic nerves and inhibit the parasympathetic nerves, it will help prevent the attack. Especially for patients with severe allergies, some minor triggers can cause physical discomfort. Coupled with the psychological fear of allergies, they often get out of hand. Therefore, it is recommended to take advantage of the advantages of caffeine and drink a cup of coffee in advance when allergies or asthma are about to attack (the patient can feel it), which has a preventive effect. In addition to the stimulating effect of caffeine, patients have a psychological sense of security that "they have drunk coffee" and are less likely to have attacks. Of course, as the saying goes “too much is not enough”, no matter how good something is, it must be “enough is enough”. Otherwise, regardless of whether you drink it before or after meals, excessive caffeine will cause side effects such as hyperpalpitations (heart beating very hard), and even trance, and unsteady center of gravity when walking. In principle, two to three cups of coffee a day is appropriate. If you drink four or five cups, most people will feel nauseous, so be careful. In principle, no more than three cups of stimulating drinks per day are recommended.