The H. pylori quadruple combination includes bismuth, one of the side effects of which is a blackened tongue, which goes away on its own when the drug is stopped. The H. pylori quadruple combination includes 1 proton pump inhibitor, 1 bismuth agent and 2 antibiotics. Bismuth is commonly used, such as bismuth potassium citrate and bismuth pectin, etc. Since bismuth itself is black, it can stain the tongue coating black and gray after taking it. This is a temporary condition and usually returns to normal tongue color after stopping the medication. In addition, bismuth can also cause ammonia odor in the mouth, black stools, etc., all of which can disappear after stopping the medication. If there are other uncomfortable symptoms, such as nausea, constipation, etc., it is recommended to consult a doctor to adjust the medication. Bismuth is prohibited for those who are allergic to bismuth, patients with severe kidney disease and pregnant women.