Have your stylist add a packet of sweet and low (over here it's the pink packet) or a saccharine tablet to the bleach or tint, it won't affect the color or the timing, but the chemicals found in those ingredients act as a buffering agent. If neither of those are handy put a clear ?soda pop? (Sprite or 7up are the ones I've tried) in a spray bottle and lightly mist your scalp (don't drench it or you'll rinse your bleach off!!) the chemicals act much the same way, and the carbonation aids in oxidizing (lightening) so you won't affect the color using this method either. (don't use a colored soda though, had a student try that at home, red food color #5 is not such a pretty color for hair...tells you how well she paid attention in class!)
I learned both of these techniques at a class at the Clairol Institute in NYC, they were given to us by one of the chemists in the lab. If you want all the details PM me and I'll dig through my stuff to find the why's and how's.
After your color ask for a moisturizing rinse, or buy one to use at home. I'm sure she could recommend one that will help relieve your itching and protect your new color so it doesn't fade or change.