Mousy, this happens to my 5 year son too! It is extremely distressing for a parent to see their child like this so I know how you feel. We found out my little boy had this kind of reaction to mosquito bite when he was 2ish. We had just moved out to the country to our heavily treed lot(therefore lots of mosquitos, blackflies) when he had his first reation to a bite on his arm. The result was 3 days on an IV in hospital with a high fever. This is one of those times in my motherhood experience that stays frozen, nothing else mattered, I stayed with him night and day, didn't sleep, you get the picture. We then saw a dermatologist and allergist who both concurred as to treatment. Always go out with lots of bug spray containing DEET. Not my favorite idea but better than near death allergic reactions. If he does get bitten, he takes Benadryl, a double dose as per the allergist. treat the bite with AfterBite, a pen type of medication which neutralizes the bite and then apply polysporin to stop any infection from scratching. The areas of eye, ears, around the nose and lips are cells that are not as tight as others areas of skin, therefore swell easier, faster and more severe than perhaps an arm or leg. My boy had a bite on his ear that swelled like a balloon and stayed that way for a long time. It is such a pain for them to have to deal with this but the allergist and dermatologist felt he would grow out of this. I would check with your doctor to be sure!