My baby seems to be allergic to mosquito bites. he has swelled up quite a bit, where he got bit. any advice for relief?

Join the club: Many (most) people are "allergic" to mosquito bites - some just have a more pronounced reaction than others. It is not unusual for me to get a reaction the size of a baseball when one gets me on the leg. It's a local reaction of histamine release. Cool compresses can help. Topical "anti-itch" treatments are generally not real helpful. Oral anti-histamines such as Diphenhydramine (benadryl) helpful.