How long it takes for the swelling to go down after a wasp sting depends mainly on the toxicity of the wasp and the degree of allergy and inflammation in the patient’s body. Wasp stings are more toxic and can cause significant localized pain and systemic symptoms, and generally do not leave a sting. Wasp stings can cause local swelling due to venom stimulation, and how long it takes for the swelling to go down depends on the toxicity of the wasp and the patient’s inflammatory response. If the wasp is less toxic, the patient’s allergic reaction is mild and the swelling and pain are not very noticeable, and the swelling usually subsides in a few hours or 2-3 days. If the wasp is more toxic, the patient’s local swelling is more severe, or complications should occur, the swelling may take longer to go down, probably about 7-10 days or even longer. After being stung by a wasp, patients should apply a weak acidic liquid rinse or vinegar gauze to reduce swelling and pain. Those who develop allergic reactions should immediately go to the hospital to prevent anaphylaxis from occurring.