Hi kit3n could be just Hives,the onset is very quick and is itchy,If it is that ask your chemist for Phernergan medicine,and check on dosage as it does have a slight sedative effect for a night time dose so they can get some sleep,hope this helps.Hives can be brought on from many things too,foods,drinks,medicines,even carpets,grass,pets,you never really know when a breakout will occur and it`s NOT contagious.Hope dd is feeling better very soon.