M.B.
We've used a topical solution in the past called "Afterbite" ... it comes in a pencil like applicator with a sponge top, and is basically ammonia (I think...) ... it does help, if put on quickly.
http://www.tendercorp.com/product.php?category=Insect%20B...#
Don't get the afterbite that has benzocaine.. I don't think that does much good.
Also.. watch out for mosquito bites... we're having a LOT of problems in Texas with West Nile Virus... including several people that have died from the severe form...