When patients have allergies caused by eating crabs and itching all over the body, they need to stop eating crabs immediately, they can first use drugs to relieve the itching symptoms, and they also need anti-allergy treatment. 1. Topical drugs: Some patients have mild systemic symptoms after eating crabs, they may only show rashes and itchy skin, so they can first use topical stove glycolic lotion, menthol lotion and other anti-itch treatments. If the itching is intense, you can also apply the appropriate dose of damphenol ointment and compound camphor cream to relieve the symptoms; 2, anti-allergy treatment: patients can choose to use paracetamol, loratadine, imipramine and other drugs for anti-allergy treatment under the guidance of a doctor; when allergy causes a rash and skin swelling all over the body, you need to promptly infuse glucocorticoids, calcium gluconate and vitamin C to prevent the condition from worsening. In severe cases of anaphylaxis, acute asthma, and laryngeal edema, timely management of breathing is needed to prevent life-threatening asphyxia. When eating crab allergy, you need to be aware that the allergen may be a foreign protein in the crab or other allergens carried by the crab, which may also exist in other seafood products, and people who are allergic to crab should carefully choose other seafood.