Mosquito bites

What’s the best way to treat mosquito bites? I don’t know how but they’re getting in my house and biting my toddlers face! I feel so bad and don’t know how they’re getting in here! I never leave my door open or anything and don’t have any other bugs. It’s not a lot of them but every once in a while I’ll see one land in my sons face! Poor thing has little bumps all over His face