It is not recommended to eat grapes directly after eating crab. It is best to eat grapes in moderation two hours after eating crab. If you eat grapes directly after eating crab it will lead to a reduction in the nutritional value of the protein and may also stimulate the stomach and intestines, causing nausea, headache, diarrhea and other symptoms. Crab is rich in calcium ions, protein and trace elements, while grapes are rich in many kinds of fruit acids, vitamin B1 and vitamin C. Both foods have high nutritional value, but the tannic acid contained in grapes will react with the protein and calcium ions contained in the crab, forming indigestible and dissolved clots that will stimulate the gastrointestinal tract, leading to indigestion, nausea, vomiting, abdominal pain, etc. Therefore, it is not recommended to eat grapes and some foods rich in tannic acid, such as persimmon, pomegranate and hawthorn, directly after eating crab. At the same time, it is also not advisable to eat cold foods such as watermelon, bananas, dragon fruit, etc. after eating crabs to avoid gastrointestinal discomfort reactions. If you eat grapes directly after eating crab, you can observe first if there is no adverse reaction. If there are serious adverse reactions, it is recommended to seek medical attention and then maintain a light diet and do not eat more stimulating foods. Eating crab is prone to allergic phenomena, and although it is nutritious, it needs to be consumed in moderation, especially for people with special symptoms, such as those allergic to crab, liver disease, typhoid, chronic gastritis, etc., so as not to aggravate the burden on the kidneys or produce adverse reactions, and it is recommended not to eat crab.