A cat’s swollen mouth can be caused by allergies, such as contact with allergens or insect bites. It can also be swollen due to external forces, such as bruises, falls, violence, etc. There may also be swelling of the mouth caused by oral disease. It is advisable for the owner to first take the cat to the vet for examination and give the doctor information on the cat’s disease history and onset to assist the doctor in diagnosis and then treat the cat accordingly after the diagnosis is confirmed.
