How do I know if my son is allergic to mosquito bites? He was bitten yesterday. Red, swollen and size of golf ball. How do I treat it?

Almost All children. Have exaggerated reactions to mosquito bites. True allergy results in hives, etc. You are describing a typical reaction to a mosquito bite...Try the onion and if it continues to be swollen and hard see your doctor as occasionally a secondary infection develops....From scratching it. Do not use the onion around the eyes.
Onion. Slice an onion and put it on the bite for a minute or two...Til the juice is dried up.. The enzymes neutralize the toxins, reduce swelling, and prevent itching. Works on all kinds of insect bites. Or you can use Benadryl (diphenhydramine) and over the counter cortisone. The onion works better.