The crab is an omnivore that likes to eat decaying carcasses of plants and animals with a lot of bacteria and viruses. Live crabs' own metabolism can fight against microorganisms and inhibit their reproduction; while after a crab dies, microorganisms will utilize its rich nutrients to reproduce rapidly, allowing the crab to rot and deteriorate to produce a variety of toxins. Eating it may cause fever, vomiting, abdominal pain, diarrhea and other food poisoning symptoms.

Crab meat also contains a histidine, after the death of the crab, into histamine. And histamine is a sensitizing substance, can make blood vessels dilated, resulting in skin, mucous membrane congestion and edema, urticaria, nasal congestion, runny nose, bronchial asthma, nausea and vomiting, abdominal pain and diarrhea and other allergic symptoms, serious also cause circulatory failure. Crabs are dying or just dying, and its inhibitions are reduced to produce this histamine and toxins