According to the principle of human gastric emptying, crabs are high-protein, high-fat and high-cholesterol foods, so it takes about four hours to empty crab roe and crab meat, and about 2 hours to absorb and transform them. Therefore, if you eat dead crab, if there is no allergic reaction of histidine decomposing histamine after more than 5 or 6 hours, there will be no problem.