My daughter is allergic to most mosquitoes. When she gets bit, the bite swells up to the size of my palm, very hot to the touch, and a white ring around it! The first time this happened, it was on her eyebrow and swelled her eye shut! After giving her benedryl per the doctor's office and the swelling did not go down (in fact it got worse) I was told to take her to the ER. They prescribed and oral medication called "atarax." It works wonders. From then on every spring I would call the pedi's office for a refill and she never goes out without being sprayed down with some sort of insect repellent. From what you described, I believe he may have a minor allergy. You may want to call the pedi just to be sure, but they will probably have you see if it will respond to Benedryl. Hope that helps.