Some dogs are allergic to bee stings. Allergic reactions can vary from mild to severe. Dogs most commonly develop swollen faces and hives. If your dog is known to be allergic to stinging insects, your veterinarian may recommend administering diphenhydramine in the early stages of the allergic reaction. Unfortunately, sometimes the oral diphenhydramine is not sufficient and examination and treatment by a veterinarian may be required.
For more information, please read the article Allergic Reaction - Insect