I personally wouldn't do anything like that before discussing your cat with your vet.  

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One drop of Afrin 24 hour Nasal spray can be applied to the nasal planum in cats.  This is usually used in conjunction with other medications.  Severe upper respiratory infection, nasal tumor, or nasal foreign body may be the main problem--these diseases require more than just nasal spray to treat.  Have your cat examined by a veterinarian.