When a bee stings, it pierces the skin with its barbed stinger and releases venom. Bee venom contains proteins that cause an immune response. The inflammation causes pain and swelling around the sting site.
Signs that your pet has been stung by a bee can include:
Whining, Limping, Swelling, Drooling, Gnawing, Hives or welts, Pain when touched. If you know or suspect your pet has been stung by a bee, closely monitor them for any reaction, especially for the first hour after the sting. The location of the sting can make a great difference in observed symptoms. If your pet was stung inside the mouth, or the bee was swallowed, they may experience: Shaking of the head, Drooling, Repeated lip licking, Coughing or gag reflex, Rapid breathing or wheezing and vomiting or diarrhea.
Swelling is the most common side effect and can be completely normal, so it’s not necessarily an indication of an anaphylactic reaction. You should, however, keep an eye on your pet when swelling occurs, especially on the neck or face. If the swelling persists or worsens after a couple of hours, contact your veterinarian. 
Severe swelling of the neck or face can interfere with swallowing or breathing. In addition, a pet may experience wheezing or other kinds of respiratory distress, difficulty standing, or seizures. In any of these cases, get your pet to the veterinarian as soon as possible.
Contact your vet right away if your pet received multiple bee stings—higher levels of venom can produce a severe reaction.
