The skin and intestinesare the two largest organs in the human body, serving as the external and internal surfaces respectively. While diseases on the external surface can be detected in a timely manner, problems on the internal surface are often overlooked.  

It looks unrelated, the health status of these two organs is intricately connected. With the continuous development of medical technology, the existence of the gut-brain-skin axis has been confirmed, and scholars believe that the health status of the intestines can also affect the condition of the skin. Based on the understanding of "skin and gut diseases being the same," the connection between the immune response mediated by intestinal flora imbalance and vitiligo has attracted scholarly attention. 

I.The "forgotten organ" - Intestinal Flora 

From 2007 to 2012, the Human Microbiome Project preliminarily reported that there are up to 1000-1500 species of microorganisms distributed in the five main parts of the human body: nasal cavity, mouth, birth canal, skin, and intestines. The total number of these microorganisms is 10 to 100 times the number of human cells, and the number of genes they encode can reach more than 300 times that of humans, hence they are referred to as the "second genome" of the human body and the "neglected organ." Due to factors such as nutrition, temperature, and humidity, the intestines have become one of the places with the richest microbial diversity in the world. The intestinal microbiota consists of hundreds of millions of symbiotic microorganisms, including bacteria, viruses, archaea, and eukaryotic microorganisms, among others. Bacteria are the largest group, and thus the intestinal microbiota is also known as gut flora. Intestinal flora participate in various metabolic activities by absorbing nutrients from the human body, are involved in the immune response of the body, and maintain the health of the body. It sounds like intestinal flora are as safe and reliable as health guardians. In reality, however, when the balance of intestinal flora is disrupted, it can also become a perpetrator.Studies have shown that when the composition, quantity, function, and distribution of intestinal flora are imbalanced, it leads to dysbiosis of the intestinal flora. Disordered flora can promote the secretion of inflammatory factors, disrupt normal immune responses, and lead to the development of diseases. This immune disorder phenomenon may affect the progression of vitiligo. 

II.How to Improve Intestinal Flora Imbalance 

Vitiligo patients, especially those with a tendency for selective eating, often have intestinal flora dysbiosis, and changes in the structure of the intestinal flora or dysbiosis may accelerate the progression of the disease. A study on a vitiligo mouse model[2] showed that oral antibiotics that change the composition of the mouse intestinal flora can significantly accelerate the pathological process of vitiligo, suggesting that changes in the intestinal flora are related to disease activity. An analysis of the intestinal flora of vitiligo patients of different age groups found[3] that the diversity of the intestinal flora in vitiligo patients is significantly lower than that of healthy people, and the relative abundance of bacterial species and the metabolic function of the flora have changed, indicating a phenomenon of intestinal flora imbalance. The study divided the patients into a minor group and an adult group for detailed research. The results showed that in the minor patient group, more than 20 genera of bacteria significantly decreased, and 8 genera significantly increased; in the adult patient group, about 16 genera of bacteria significantly decreased, and 7 genera significantly increased. In both patient groups, the top three genera of bacteria that significantly decreased are all beneficial bacteria that can enhance the function of intestinal epithelial cells, maintain intestinal homeostasis, promote the development of regulatory T cells, and have anti-inflammatory effects; the top two genera of bacteria that significantly increased in both groups are pathogenic bacteria. They can damage the intestinal barrier function, leading to increased intestinal permeability in patients, triggering a series of inflammatory and immune problems. The intestinal flora can regulate the host's immune system and participate in the occurrence and development of inflammatory diseases. The reduction of beneficial bacteria and the increase of pathogenic bacteria in the intestines of vitiligo patients change the normal structure of the intestinal flora. This imbalance can disrupt the patient's intestinal barrier function, leading to increased intestinal permeability. This allows antigens from the diet, pathogens, intestinal bacteria, and bacterial toxins to escape into the blood, further activating the immune system, promoting the massive secretion of inflammatory factors, causing systemic inflammation, and aggravating the immune imbalance of vitiligo patients. Immunity and inflammatory responses play important roles in the onset of vitiligo. Intestinal flora disorders can lead to an imbalance of the body's immune homeostasis, inducing inflammatory responses, and may be involved in the onset and development of vitiligo. Therefore, patients need to pay attention to the phenomenon of intestinal flora disorders during treatment, detect it in a timely manner, and treat it promptly. 

III.Subsequent Stabilization, Prevention is Better than Cure 

Since intestinal flora disorders can affect the progression of vitiligo from metabolic and immune aspects, then regulating the intestinal flora and maintaining the balance of the intestinal microecology should also have potential in the treatment of vitiligo. Diet is one of the most important factors affecting the composition, diversity, and richness of the intestinal microbiota. Long-term changes in dietary composition can effectively change the composition of the intestinal flora and intestinal metabolic activities. The following foods are beneficial for regulating the intestinal flora: 1. Edible fungi Moderate intake of edible fungi such as Hericium erinaceus, Agaricus bisporus, and Pleurotus ostreatus, which contain nondigestible active polysaccharides, can effectively promote the growth of beneficial bacteria and inhibit the reproduction of pathogenic bacteria[5]. 2. Cereal foods Studies have shown that dietary fiber that is difficult to be absorbed by the small intestine can be quickly utilized by intestinal microorganisms during the fermentation process and selectively promote the proliferation and metabolic activity of beneficial bacteria[6]. Therefore, patients should moderately consume some brown rice, whole grain flat noodles, brown rice rice noodles, etc., which have a positive impact on the balance of the intestinal flora. 3. Fermented foods Fermented foods such as yogurt and cheese are rich in probiotics. Probiotics can not only improve the flavor of food, extend the shelf life of food but also regulate the balance of the intestinal flora, lower cholesterol, and bring specific health benefits. Although there is currently no evidence to confirm that intestinal flora disorders can directly cause the onset of vitiligo, the series of inflammatory responses and immune disorders caused by intestinal flora disorders are very likely to indirectly promote the onset and development of vitiligo. Timely prevention, regulation, or may be able to assist in controlling the progression of the disease.