Giant swelling from mosquito bites in child?

My son swells up HUGE from mosquito bites. If it bites near an ear....double size ear. If it bites near an eye...swollen almost shut. Arms and legs swell like a ping-pong ball at the site. So, here is a multi-part question.
1. Best way to prevent bites?
2. Best way to treat bites?
3. How do you know when to see the pedi when every bite becomes huge, hot, and red.

Background: 3 kids, he's 5 and in the middle. He's the only one who reacts this way. We live in the sticks. His discomfort level is low, it's the appearance that is so SHOCKING! I'm worried because I'm especially afraid I won't be able to discern between a reaction and an infection

Hes allergic to mosquito bites (I am too) Try to keep him covered in bug spray as much as possible. The other remedies posted will probably work as well. Next time you see your pediatrician ask him/her what the best course of action is.

Give him thiamine(vitamin b-1) you can get it in liquid form from your pharmacist. If he does get bit give him benadryl. Only go to the pediatrician if his throat starts swelling shut.

Pay Attention. Anti-histamine is for the bite along with children's aspirin.

Break an Adult tablet into four pieces of an anti-histamine, like Allergy pills, and give him one piece of the four. Give him one child aspirin, or child tylenol, child advil.
If you only have over the counter adult Tylenol or Advil break it up into four pieces and give him one piece with the one piece of the Anti-histamine like Benedryl or what ever you have for your hay fever pills for Allergies.

One quarter of the adult tablets should be enough for the child.

If he can't swallow take him to the EMERGENCY ROOM as quickly as possible. Don't Waste Any more Time!