The preservation period of wakame is about one year, and after three years it may harbor more bacteria, leading to spoilage. Nitrates in expired wakame may be converted into toxic nitrites, which may cause a toxic reaction after ingestion, leading to nausea, vomiting, abdominal pain, diarrhea and other symptoms. Consumption of ingredients in life should pay attention to the freshness period, do not eat after the expiration date.