8 month old son has loud stuffy nose at night or when lying on side. have cats, but no other allergy symptoms. 3rd week now. happy healthy otherwise.

Possibly allergies..: Given your story, your son could very well have allergies. It is relatively uncommon for viral upper respiratory symptoms to last 3 weeks unless a second one occurred. Seasonal allergies are very unlikely at this age but perennial allergens such as cats, dogs, and dust mites could affect him. I suggest that you discuss this with your pediatrician and possibly an allergist for further evaluation.

URI vs. allergy: Cats represent the most common allergenic domestic animals within households. The cat saliva is the most potent protein component producing allergy symptoms. This child's symptoms may also represent a viral upper respiratory infection. Start with saline nasal sprays, anti-inflammatories such as Aspirin or ibuprofen. If no improvement soon see an otolaryngologist to evaluate the nasal anatomy, etc.