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Why does my dog have a red, itchy patch on its mouth for months?

Updated On September 23rd, 2025

Pet's info: Dog | Mixed Breed Large (61lb +) | Male | neutered | 2 years and 8 months old | 62 lbs

Hi there! Our dog, Trooper has had this red patch on the side of his mouth for about 2/3 months. It has not changed much in size, it does not bleed or ooze, but it does seem to itch sometimes. There has a been a time or two that he has scratched it and it has left a little scratch. We have dried eliminating grains, using Benadryl, switching dog food and water bowls, washing them more often, and applying antibiotics. Any other suggestion? No other dogs in the home, up to date on vaccines.

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1 Answer

Most Helpful Answer

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Answered By Ricardo Fernandez, DVM

Veterinarian, Veterinary Oncology Resident

Published on August 11th, 2019

Thanks for using Petco Pet Education Center, formerly Petcoach! This is possibly due to allergies. It really comes down to figuring out what is causing his allergies so that they can be treated or the specific allergen avoided. A secondary infection is likely and also needs to be addressed. There are many things that can cause allergies though in most cases they can be broken down into 3 big categories: flea, food and environmental allergies. Allergies are usually worked up in a stepwise fashion starting with flea allergies as this is the easiest and cheapest to take care of. If not on a flea preventative, then it would be a good idea to get started on one. If already on one then it would be a good idea to change to something else (there are many new products out in the market). If not improved in 1-3 months then it is time to move on and check for food allergies by switching to a novel diet (new protein and new carbohydrate). If that does not seem to be the issue then you are left out having to check for environmental allergies which require blood and/or skin tests. Allergies can be very frustrating to deal with at first but so rewarding at the end when we are able to treat them effectively!

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