Personally, I don't premedicate for a normal cleaning.  If you want to, I would take an extra dose of H1/H2 (for example, 10mg of Zyrtec plus 150mg of Zantac).  The only time I premedicate for the dentist is if we're doing something more serious... like last December when I had to get two crowns.  In addition to the H1/H2s, I took 10mg of valium about an hour before my appointment.  It really helped!  I also listened to calming music during the drilling.

Heather

You should check the list of local anesthetics that are less problematic for mast cell patients.  My list says that Lidocaine, Bupivacaine, Mepicacaine, Prilocaine, Levobupivacaie, and Ropivacaine are less likely to cause problems. Avoid Benzocaine, Chloroprocaine, and Tetracine.

I ask for a local anesthetic that does not have epinephrine in it, because it causes me to have symptoms.