Unfortunately, there aren’t any home remedies for facial swelling in dogs. This is because the most likely causes of facial swelling are allergic response, infection, or injury, all of which require veterinary attention.
Facial swelling of any kind should be assessed by a veterinarian immediately.
Allergic reactions that begin with facial swelling can progress to difficulty breathing, anaphylactic shock, and even death. It is best to not to self-diagnose, as delaying veterinary attention during a possible allergic reaction can be life threatening. If the facial swelling is due to something else entirely, such as an abscess or dental disease, these are also conditions that need veterinary attention, albeit less urgently.
It’s a good idea to keep Benadryl on hand for possible allergic reactions. This is the same Benadryl we use in humans (make sure there are no additional ingredients; just Diphenhydramine). Ask your veterinarian for an appropriate dose for your dog.
Pro Tip: Keep some Benadryl on hand, but any case of facial swelling should be addressed by a veterinarian asap.