I've been AWOL for a while, sorry to come back with a health question. My darling Sis' new husband's cat (Mr. Whiskers) is a 14 year old Oriental cat who has chronic Upper Respiratory Infection. It can be controlled with antibiotics, but they've noticed Mr. Whiskers seems to react badly to the meds otherwise and they're worried about repeated use. They asked if there was an herbal supplement or treatment that was easier on a senior cat. I drew a blank, but thought some of the experts here might have some suggestions. Please?

Thank you!