How to cure hives on toodler

Hi, does anyone know how to cure hives on Toodler? This is the first time my Toodler get hives I dont know how he get it. He ate 1 spoon of beef soup yesterday night and one butter sunshine bread he used to eat these food but nothing happens. Yesterday when I gave him those food today his body start. Appearing patches of mosquito looks bite mark now he keep scratching now it spread till his back. What am I suppose to do?