I was on a trial and am currently in follow up and I use the antihistamine Promethazine Hydrochloride (Phenergan) daily and have done since I started treatment. I have also used the one you mention (Fexofenadine Hydrochloride or Telfast) whilst txing.
When I started the trial I had to tell them about all existing meds and neither of those antihistamines were contraindicated with the tx meds and my trial doctor said it was OK to continue using them during the trial and the following SOC treatment.
I don't anything know about whether it may affect SVR and I certainly hope it doesn't.
My local GP gave me Loratadine (another that says to check before using if you have liver disease :-(... but he said it's okay and I note the 'medicmommy' used in on tx also); I haven't checked with my Nurse (forgot to yesterday), but thanks, Epiphany, for clarifying about the Telfast.
Emi - same thing happening in NZ, same dates; it hit me last week!!
P.S. - I also alternate using a 'saline rinse bottle' which I find really good and stops me having to use the meds so often. Good luck with that - I was dreading this time of year also.
Thanks for the information and I guess most of these branded meds are similar. Really bad season for allegies K, pollen count has been extreme x 2 for 2 weeks. The saline rinsing sounds like the go and I will try. I had considered filling the bath up and breathing through a snorkel or sleeping in the fridge, but the saline sounds practical. Emi