We have never had to take our daughter to the ER (knock wood).  WE have given the shot on many occasions.  She responds so quickly to the shot that there has been no need to take her.  We do call her doctors and let them know what is going on.  This is why you shouldn’t be afraid to give the shot as it can keep you OUT of the ER and all the cooties in there!!!  They always say, if she continues to vomit/diarrhea, high fever or lethargic bring her in.  She has never vomited more than twice at one illness.  So I guess as long as they are acting normal and keeping fluids with out a high fever staying home is okay but let your docs know what is going on.  We have never been told that the shot lasts 24 hours.  Is yours solu cortef?  It is a huge dose but it is still short lasting.  I still give meds after a shot.  Also, consider each person with CAH responds differently when ill.  Be cautious until you get to know how your child will respond.  WE are told to triple dose in fevers etc.  Some say double.  Ask you endo.  Good luck.  Julia