Do you have an allergist or mast cell doctors office you can consult with for specific pediatric doses and a plan for her?

That would be ideal and it is very critical she be premedicated appropriately. Some might even use steroids. I would put a call in to their office.

There is an adult protocol for contrast studies and procedures on the TMS site that generally recommends doses 12 and 1 hour prior of steroids, H1 and H2 antihistamines, but it needs to be tailored to the specific situation and pediatric dosing as I'm sure you know

http://www.tmsforacure.org/documents/ER_Protocol.pdf

On page 4

Most recommend the study should be done in a hospital or clinic where they have a crash cart/emergency support closeby in case of any reactions.

GOOD LUCK

Thanks!  My daughter is 31 yrs of age.  I will have her call her rheumatologist to obtain steroids for the procedure madelyn
She does not have an allergist or mast cell doctor.  she has a rheumatologist for "some sort of autoimmune disease process (undefined--she is positive for RNP antibodies, though the levels are not very high)  and she now is seeing a neurologist.  She is in graduate school in NYC;  her internist is in cincinnati, oh. She has not seen him for several years now.  
I called Dr. Cassels office and received an "intake form" in the mail stating one will not be seen without a written referral from a physican, with a confirmed or strongly suspected diagnosis of cutaneous or systemic mastocytosis.  Otherwise one will not be accepted.  In bold letters:  SELF REFERRALS ARE NOT ACCEPTED.
There is a listing of tests that should be done prior to the referral.  Sheesh!!! No one my daughter or I have talked to has ever heard of mast cell activation disorder, and no one wants to read the articles I have offered either.