Hello I am Dr. Joey. Thanks for trusting me to help you and your pet today. I am a licensed veterinarian with over 16 years of experience. I look forward to working with you.
I'm sorry Kato is experiencing this. There are many possible causes for upper respiratory congestion. It could be due to allergies to something in the environment, but probably not the water. If allergies, then more likely to be a grass, pollen, leaf, mold or something such as this. Alternatively, he may have an actual infection (bacterial or fungal) in his nose. Some areas have very high fungal infection rates. Or, this could be due to a poly/tumor or even foreign object in his nose.
The absolute best next step for him is an exam with your area veterinarian. Some testing may be indicated such as radiographs (X-rays) or even sedation to view up his nose (endoscopy is best) and flush this for samples.
In the meantime, if he was my patient I might recommend you try an antihistamine such as Benadryl for him (diphenhydramine) which you can purchase at any people pharmacy at a dose of 1 mg per pound and then you round up to the nearest 25 mg. This may help improve him if this is allergies.
I am at a point I need to know what questions you have. I hope that the information I provided has been helpful.
Please let me know if for any reason you need further clarification, have more questions, or were expecting a different type of answer.
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