Antibiotic-associated diarrhea (AAD) refers to diarrhea secondary to the application of antibiotics and is a relatively common adverse drug reaction, the incidence of which varies from 5% to 39% depending on the type of antibiotic. Secondary diarrhea caused by the application of antibiotics can be classified as simple diarrhea, colitis or pseudomembranous colitis, depending on the degree of the disease. Pseudomembranous colitis is a serious condition with pseudomembrane formation in the colonic mucosa, which can lead to complications if not recognized in time and given reasonable treatment, with a mortality rate of 15-24%. The occurrence of this disease, the more consistent view is that antibiotics disrupt the natural ecological balance of intestinal flora, that is, a significant reduction in physiological bacteria, while the number of aerobic bacteria and parthenogenic anaerobic bacteria increased, which is mainly related to the development of pseudomembranous colitis is difficult to identify Bacillus cereus (CD). Almost all drugs that can fight bacteria can cause AAD, with lincomycin, azithromycin, and ampicillin being the most common. In addition, the cephalosporin family and penicillins are also commonly seen, with aminoglycoside antibiotics occurring less frequently. However, antibacterial agents against Mycobacterium tuberculosis, fungi, and antiparasites have not been reported. The risk factors for the development of this disease, in addition to the different antibiotics and the duration of antibiotic application, are also related to the patient’s age (<6 years or >65 years, severity of underlying disease, past intestinal disease, immunosuppression, length of hospitalization, trauma, surgery, nasal feeding, etc. The onset of AAD can occur after 4-10 days of antibiotic application, but there is great variability, with the shortest onset occurring within 4 h of administration. The onset of AAD can occur 4-10 days after the application of antibiotics, but there is great variability, with the shortest onset occurring within 4 h of administration. The onset of AAD has been reported after 2 to 7 days of oral ampicillin administration. In particular, the onset of symptoms has been reported to be delayed in at least 1/3 of patients with AAD until the antibiotic in question has been discontinued, or even 1 to 2 weeks after discontinuation. Many antibiotics, especially those taken orally, can cause gastrointestinal side effects of varying degrees, such as nausea, vomiting, diarrhea or loss of appetite, and even affect liver, kidney and hematopoietic functions. The reason for this is that in addition to the chemical irritation factor (chemical irritation is related to the dose), broad-spectrum antibiotics can cause dysbiosis in the body and lead to secondary infections is another important factor. Secondary infections, also known as dysbiosis. Under normal circumstances, people are in a large microbial survival environment, the human body’s skin mucosa and the cavity with the outside world, such as the mouth, nose, throat, intestinal tract, etc., are parasitized by a certain number of bacteria, these numbers of bacteria, and the human body both interdependent and mutual constraints, not only harmless, but beneficial to the human body. The normal flora of the intestine not only plays an important role in promoting the digestion and absorption of food, but also has a strong inhibitory effect on pathogenic bacteria that are harmful to human health and can effectively inhibit their growth and reproduction, which is very important for the human body and is known as micro-ecological balance in medicine. The application of antibiotics, especially broad-spectrum antibiotics, both inhibits sensitive bacteria in various parts of the body and allows drug-resistant bacteria to take advantage of the opportunity to multiply and grow in the body, leading to a dual infection. In other words, originally, antibiotics were used to kill pathogenic bacteria, but as a result, they were faced with more serious bacterial infections, in which drug-resistant Staphylococcus aureus and gram-negative bacilli were the main pathogens of the duel infections. The duel infections caused by drug-resistant Staphylococcus aureus and others are mainly enteritis, and it follows that the duel infections caused during the application of broad-spectrum antibiotics often aggravate diarrhea. In addition, the application of broad-spectrum antibiotics inhibits many bacteria in the intestine, and some of these bacteria have the ability to synthesize vitamin B and vitamin K. Therefore, the dysbiosis may lead to vitamin B complex deficiency, and gastrointestinal symptoms such as nausea, vomiting and diarrhea may occur.