Not one of my kids, but me.  After an allergy shot.   

DS had anaphylaxis to his allergy shot while still at the allergist's office.  The nurse didn't seem concerned when I reported his symptoms to her (limp/wilted, lethargic, chest pain), but went and told the doctor.  At that point the nurse came back at a full run with the doctor close on her heels since the doctor recognized the symptoms as an EMERGENCY when the nurse told her.  They had an emergency treatment room with crash cart, so they chose to treat him in-house.  He was given epi and a big dose of liquid Zyrtec and kept for observation.  Like CM, due to proximity to the hospital, we were comfortable with this treatment and our subsequent return home.

Minor anaphylaxis (grade 2-3), yes.  Twice(?)  They had epi drawn and a crashcart on floor, and could transport into ER in pretty much seconds (next door) so we were not terribly concerned with handling. 

Similarly, handled in-office; benadryl and observation.  We suspect that our relative experience and home proximity to ER was also a factor in letting us go home after a few hours.  Allergist has "called in" at home afterwards, too-- to check up on biphasic symptoms and our follow-through.

But similarly, this was the point at which allergist stopped telling us that "aerosol sensitivity isn't real."

Real turning point in our relationship with the allergist, in fact; after that he's been convinced that we are NOT over-reactive, histrionic, or somehow provoking somatic symptoms with our stress.

Asking because one of mine did and he handled it almost verbatim by anaphylaxis grading and emergency action plan. What we didn't do was call for ambulance and I'm revisiting that decision. On one hand competent allergist and allergy nurses with anaphylaxis expertise and no unsavory ER surprises. On the other no ER equipment.

Please also include if it had an effect on allergist executed care from there on. Ours had a sort of medical rebirth moment where it rewrote what he "knew" about thresholds.