[onyx'girl]

You can have allergy tests run to see exactly what she is allergic to. Then they will make up a serum for her and give injections to desensitize her. I'm doing this for Onyx right now, so far-haven't seen results but it may take a year to get her system to "ignore" what she is allergic to.
Vitamin C is a natural anti-histamine, so I would supplement with that and maybe give benedryl for the itching.

 

[onyx'girl]

Vitamin C can give the dogs the runs, so introducing it slowly upping the dosage over a week or two is best. I doubled Karlo's amount when he was going thru pano, and it looked like cement coming out.
I had the Heska test run and they did test for many grasses, molds etc.

 

[onyx'girl]

On the vitamin C, can I use what I have on hand here for us? Does the dosage depend upon weight?

I use human grade 500mg. Start with that and slowly up the dosage to 2000mg(split between meals) daily over a week or two...so eventually the dosage is 1000mg am and pm. If the dog is over a year EsterC is easier on the gut(it contains more calcium than regular C so not appropriate for young pups) Dosage would be the same for the EsterC.

 

[onyx'girl]

At her age/size I would only 1000mg for a couple of months til she gets a bit bigger, starting at 500mg for a week or so and then 1/2 pill am & 1/2 pm

 

[onyx'girl]

I hope this is the last time she & you have to deal with this. In her short life, she's had her share of vetting!
Probiotics should help, hopefully. If you have access to raw(frozen) green tripe, that has natural probiotics and digestive enzymes. Maybe supplement her meals with that or give it mid-day.
Healing thoughts for Shasta!!