Major Swelling after MMR

My son had 2 vaccinations and he reacted to the MMR quite bad. His arm swelled up twice it's normal size from the elbow to sholder. It was hard, red and hot and he complained of it being very itchy. He also reacts in a similar way to mosquito bites but not sure if they're related. Any ideas ??

Also, I've noticed that with each MMR his reaction gets worse. Are they egg based and should I have him tested for allergies to egg ? Tweet