A wasp sting occurs when a wasp injects venom through its stinger into the skin of a person or animal. This venom contains proteins that can cause pain, swelling, and redness at the sting site. Most people experience mild symptoms, but some may have allergic reactions that require medical attention. The pain from a wasp sting is usually immediate and can last for several hours. To treat a sting, it is recommended to clean the area, apply ice to reduce swelling, and take over-the-counter pain relievers if necessary. In severe cases, an epinephrine injection may be needed for allergic reactions.