There is truth in that statement! As a doctor, my answer is so. And I often tell my friends, relatives and patients that most of those who have low immunity and are prone to colds and allergies have to do with eating and dressing too well. Oh, I can see from their eyes and expressions their surprise that this is coming from a doctor’s mouth. Don’t they say that diseases come from the mouth? How can I be such an unhygienic doctor! I said with a smile: “If you don’t eat it, you won’t get sick” and “disease enters through the mouth” are dialectical unity, they are not contradictory. If a doctor really understands medical immunology, he or she will know the scientific spirit contained in this saying left by the old ancestors. Where does a person’s immunity come from? Before answering this question, I would like to draw your attention to a common sense of life: wild animals and wild flowers and plants in the natural world are inhabited by the wind and rain, while flowers in greenhouses and ornamental plants are often inexplicably withered, and children in rural areas often run wild in the mountains and wilderness, and are not as clean and well-dressed but not prone to disease. The more pampered and hygienic children in the city are, the more they have to catch a cold and fever with slight changes in climate and environment. Why is this? It turns out that human immunity is not directly obtained from nutrition, but relies on the stimulation of various antigens inside and outside the body, stimulating the body’s immune system to produce. These antigens include the components and metabolites of various pathogenic microorganisms (such as viruses, bacteria, etc.). Without their stimulation, the body cannot acquire specific immunity. When very small amounts of bacteria and viruses repeatedly stimulate the organism, these immune systems produce corresponding specific antibodies and sensitizing lymphocytes against them, and when a large number of bacteria and viruses invade, they can be quickly mobilized for targeted defense. Here, these very small amounts of bacteria and viruses are equivalent to the role of “vaccination” for the human body. If the internal and external environment of the human body is “clean” for a long time, on the one hand, the normal defense system of the human body cannot be mobilized, and on the other hand, the human body’s defense system is “dormant” for a long time, which can cause immune dysfunction and lead to non-recognition. On the other hand, the long-term dormancy of the body’s defense system can also cause immune dysfunction, resulting in non-recognition of “invaders” or “indistinguishability between the enemy and me”, resulting in all kinds of wrong immune rejection, inhibition, allergy, etc. The core of our ancestral saying, “Eat clean, don’t get sick”, is that we should not be too particular about our diet, which can maintain our health. This is similar to our modern immunology theory and can be explained scientifically. Of course, not dry, not that the spoiled food can also eat, but that the daily food does not have to do sterile cleanliness, not too deliberate to endless cleaning, disinfection, some people love clean love to the degree of cleanliness, the requirements of food cleanliness to the point of demanding, which is not good. Of course, do not go to the other extreme, “not dry, eat no disease” as an excuse for not being hygienic, deliberately to unclean, unclean for unclean, which is also undesirable.