Q. Cats left eye and nostril run almost constant, sometime nostril has a bloody discharge
DAVID ELBEZE, DVM, MRCVS
A. If it's only one side (the nose and eye) it's unlikely to be an upper respiratory infection. It's more likely to be either a tooth abscess or a foreign body stuck in the left nasal cavity.
Bring your cat to the vet which will check his mouth, hopefully it will be a tooth problem as it is simpler to treat.
DESTINI R. HOLLOWAY, DVM
A. Your cat is displaying classic signs of rhinitis. This can have many causes the most common being feline herpesvirus and calicivirus, which over time can cause erosion of the nasal passage creating epistaxis (bloody discharge). However due to your pets age I would use caution here and realize that there are also other possible causes of bloody discharge including fungal infections and neoplasia. I would highly recommend you get testing done at your local vet of the nasal passage (i.e. Rhinoscopy, culture/sensitivity of the nasal discharge) to help identify the culprit. This is the most direct approach to finding out what this is so that you can treat it appropriately.