In daily life, seafood and fruits can usually be consumed at the same time. So when you make sure the crab is cooked and the watermelon is not contaminated, the two can be consumed together in small amounts and there is usually no significant adverse reaction. Some people believe that the pentavalent arsenic in crab will react with the vitamin C in watermelon to form trivalent arsenic, or arsenic, which is toxic to the body. However, in reality, this reaction is only possible when the body consumes 20-100 kg of crab at one time, and this does not usually happen with normal consumption. Watermelon contains vitamins, phosphorus, potassium and other nutrients needed by the body, while crab is richer in protein, calcium, phosphorus and iron, so eating both in moderation can help the body replenish its nutrients and the nutrients in them usually do not conflict significantly. If some people experience gastrointestinal discomfort such as vomiting and bloating after eating watermelon and crab together, it may be due to the fact that the crab is not fully cooked, the watermelon is consumed in excess or the watermelon is too cold and stimulates the stomach and intestines, resulting in gastrointestinal discomfort. Allergies can also lead to the above symptoms, so you should avoid touching crabs again. If the adverse reaction is weak, you can first observe your body for abnormalities, which can generally be gradually relieved, but if the discomfort worsens, it is recommended to seek medical treatment as soon as possible. In addition, patients who have gout disease themselves are advised to eat crab with caution, because the high purine content in crab may trigger or aggravate gout.