Keep an eye on it
What it can look like. A general, vet-reviewed example — signs vary and this is not a diagnosis. When in doubt, ask your vet. 
Face rubbing in dogs
Clinical name: Facial pruritus
Rubbing the face and muzzle on carpet, furniture or with the paws.
Where it shows upface · muzzle · eyes
Typical patternMuzzle and around the eyes.
Linked allergy typesEnvironmental (atopy) · Food allergy · Contact allergy
Food vs environmentalNon-specific — common in both food and environmental allergy.
What you can do
Note if it follows meals or time outdoors.
Don't confuse it with
Other causes a vet will want to rule out: eye irritation, ear pain, dental pain.
This is educational information, not a diagnosis or treatment plan. Always see your veterinarian about your dog's health.
Related signs
Itching & scratchingKeep an eye on it
Frequent, restless scratching that the dog can't settle from — the hallmark of allergy.
Excessive lickingKeep an eye on it
Repetitive licking, especially of the paws and legs, often to the point of wet fur.
Chewing & biting at skinKeep an eye on it
Gnawing or nibbling at the skin, sometimes leaving damp or raw patches.