Estrogen cream + claratin?

I'm wondering if I do happen to need vaginal estrogen but also get mast cells flaring up. would it be a good idea to take claratin alongside the estrogen cream?

that way the mast cells can calm down while the estrogen does its work healing tissues?

background:

I was in remission for a long time, only short bouts in the past. This 7mo IC flare started after taking letrozole (which block estrogen) for two cycles for fertility. also got a tailbone injury simultaneously some how. I think the low estrogen also made me more hypermobile and anyway.

I'm doing pelvic floor pt. IC diet works really well. if physical activity flares it up ever the heat pads usually work to calm it down.

sex has been a bit more uncomfortable though and id like to heal this bladder already so I can eat healthier again which is why I'm trying estrogen cream. I'm 36 years old.