The food additive agar is a commonly used thickener and coagulant that is widely used in food processing. However, there are some potential hazards associated with agar. First, agar may cause allergic reactions. Some people may be allergic to ingredients in agar, such as fish gelatin proteins, leading to adverse reactions such as itchy skin and breathing difficulties. Second, agar intake may affect the digestive system. Due to the gelatinous nature of agar, excessive intake may lead to digestive blockage or intestinal discomfort, triggering problems such as abdominal pain, bloating and constipation. In addition, agar may contain heavy metal residues. Raw materials containing heavy metals may be used in the production process. Without stringent testing and treatment, heavy metal residues in agar may exceed the safety limits, posing a potential threat to human health. To summarize: The hazards of agar are mainly allergic reactions, digestive problems and potential heavy metal residues. Careful selection should be made when consuming food to avoid excessive intake and pay attention to the safety instructions on the relevant food label.