The tonsils lie within folds of tissue on either side of the throat. The tonsils perform immune functions, helping to fight infection in the head region. Anything that causes inflammation and/or infection in this area will cause activation and enlargement of the tonsils. While tonsillitis refers to inflammation of the tonsils, it does not refer to a specific cause. Tonsillitis rarely occurs without an underlying cause such as viral, bacterial, and fungal infections, tumors, chronic cough, and periodontal disease. Dogs with tonsillitis may hesitate to swallow food due to the pain caused when swallowing; they may swallow repeatedly and become lethargic. To diagnose tonsillitis, your veterinarian will do a visual inspection of your pet’s throat. Some pets may need to be heavily sedated to allow thorough examination of the throat. An underlying cause should be investigated and treated specifically. Typically, surgical removal of the tonsils is only necessary when a tumor is present.