Hello, my name is***** and I have over 20 years of experience as a veterinarian. I am sorry to hear that your girl has a somewhat firm swelling under her right eye that is causing her eye to close half-way.
Is the swollen area on her cheek on the area just below her eye? (see the pictures of the dogs in the links below)
If so the most likely cause of it is actually a premolar tooth root abscess that has fistulated through the bone
and into the tissue under her skin. The roots of the upper premolar teeth end up just below the eye and if the tooth root becomes infected the infection often travels through the soft tissue around the root and drains out through the face. As the infection worsens we can see quite a bit of swelling on the face. The tooth crown may look normal in the mouth, as it is the root that is infected, but sometimes we can see how the infection entered via a crack or chip fracture by looking at her teeth.
The other common cause of sudden swelling and redness is an allergic reaction. This can be from an insect bite or sting, pollen, or plants (much less common in dogs). Sometimes we never figure out the cause of the allergic reaction.
Treatment is based upon stopping further allergic reaction with antihistamines like Benadryl and sometimes cortisone if the reaction progresses.
You can give her Benadryl (diphenhydramine only don't use the combination products with decongestants or acetaminophen as they can be toxic
for dogs) at 1mg to 2mg per pound of body weight or one 25mg capsule per 15 to 25 pounds of body weight orally every 8 hours. You'll need to give it for at least 72 hours (3 days) to allow the allergen time to clear. If you stop too soon the reaction will recur.
Dogs take a really high dose compared to people, so don't let the amount worry you. They require more than we do. This may make her a little sleepy. And then you'll need to watch her closely for any progression of symptoms. That would include difficulty breathing, vomiting or diarrhea.
The swelling should resolve slowly over the next 12 to 24 hours with the use of Benadryl if this is related to an allergic reaction. If her swelling resolves then you know this is an allergic reaction and if that's the case you should keep Benadryl on hand at all times.
If you'd like to get the swelling down quicker with an allergic reaction you can have her regular veterinarian check her and give a cortisone injection which will lessen symptoms faster.
But if she seems to be doing well then I would just call them and let them know so it is on her record for future reference.
Other possible reasons for what you are seeing other than an abscessed premolar tooth root, or an allergic reaction include an infected or blocked salivary gland, a type of cancer in her lymph node (lymphoma
) or a bite or scratch wound that has become abscessed/infected. If your girl isn't improving with antihistamines then she needs to see her veterinarian for some testing to determine why she has this swelling, and appropriate treatment.
If she isn't improving she needs to see her veterinarian for an examination and antibiotics and she will likely need a tooth extracted. This isn't an emergency as long as she is still eating and drinking well. They can put her on pain medication and anti-inflammatories as well which will decrease the swelling near her eye.
Please let me know if you have any further questions.