Is it toxic if seaweed egg drop soup turns green?

Generally, it is a normal phenomenon for seaweed egg drop soup to turn green, and this does not necessarily mean it is toxic. However, whether it is safe to eat should be judged based on specific circumstances. If in doubt, it is recommended to consult a healthcare professional in advance. Detailed analysis is as follows:

Seaweed naturally contains chlorophyll and phycocyanin. When heated, the stability of chlorophyll decreases, and it may react with proteins from eggs or minerals in the soup, potentially causing the soup to appear green. This reaction is a normal food interaction that does not produce toxic substances and typically poses no harm to health when consumed. In particular, when fresh seaweed and eggs are used without any other unusual ingredients, discoloration to green is usually harmless.

If the seaweed has been improperly stored (e.g., exposed to moisture or mold), or if spoiled ingredients have contaminated the soup, turning green along with unpleasant odors, cloudiness, or絮状物 (flocculent particles) may indicate microbial growth or toxin production. In such cases, the soup should not be consumed to avoid gastrointestinal discomfort. Additionally, using low-quality or contaminated seaweed may also lead to abnormal green discoloration due to the presence of harmful substances.

When preparing seaweed egg drop soup, always use fresh seaweed and eggs without any off-odors. If the soup turns green and shows any abnormal characteristics, it should be discarded immediately—do not risk consumption.