Hi Dr. Jean, One of my cats will start sneezing seasonally, with the discharge gradually changing from clear to yellow to green. None of the other cats are affected by any similar symptoms at all - it's confined specifically to him, even though they regularly have close contact. This began when he was about 8 or 9years old; he's 12 now. I've had him to 2 different vets for it; they both say it's probably sinusitis caused by irritation from seasonal allergies (easy for me to understand- I have the exact same problem myself, and we live in a climate where various allergens are high year-round). An extended course of antibiotics and antihistamine (chlorpheniramine) will clear it up for a while, then it comes back again a few months later and we go through the cycle again. Our vet said we may need to keep him on the antihistamine long-term. Health notes: At his most recent visit the vet noted that he needs his teeth cleaned again, but we're waiting until the infection has cleared to do his dental. He's on dry urinary s/o because of a history of urinary blockage (I've read from your other posts that we need to change that - if you have recommendations for a good canned option for him I'd love to know what you recommend). He also has a very sensitive stomach - s/o is the only urinary food we've found that doesn't give him diarrhea. He's an indoor cat, though he was allowed outdoors when he was younger. He weighs 15 pounds; he's about 1/2 to 1 pound overweight, according to the vet. He's been vaccinated regularly throughout his life, except for the last couple of years now that I've backed off from annual vaccinations. Do you have any ideas or recommendations for him?