Bismuth poisoning can be caused by accidental ingestion of large amounts, excessive medical use, or long-term use of bismuth. Bismuth poisoning in children is mostly caused by the use of large amounts of bismuth subnitrate to treat diarrhea. Due to the action of intestinal bacteria, bismuth subnitrate can be oxidized to nitrite, so symptoms of dual poisoning of bismuth and nitrite may occur. The lethal dose of oral bismuth subnitrate for children is about 3 to 5g. Excessive intravenous or intramuscular injection of soluble bismuth salts can lead to acute poisoning. Insoluble bismuth salts (such as bismuth subcarbonate, etc.) are often used as oral drugs or topical preparations for the treatment of gastrointestinal diseases. Although the amount absorbed is very small, large amounts or long-term use can also lead to bismuth poisoning. Lactating women apply cod liver oil bismuth multiple times due to nipple rupture, and infants may be poisoned by sucking in large amounts.