Allergy is a type of metamorphic reaction in the body. Joint pain after a metamorphic reaction is caused by an abnormal immune response in the body, where the immune cells attack the normal tissues around the joints, causing tissue damage. An anaphylactic reaction is when the body is exposed to an allergen, such as pollen, seafood, dust, alcohol, etc., and the body treats the allergen as a harmful substance and removes it, causing a series of reactions. Joint pain after an anaphylactic reaction may be due to the fact that the body’s exposure to the allergen causes the body’s immune response, and the immune cells attack the normal tissues around the joints, such as the articular cartilage, synovium, tendons, etc., causing damage to the tissues, and thus pain in the joints. If the pain persists after an allergic reaction, it is recommended to consult a doctor and follow the doctor’s instructions.