sounds like allergies to me exspecially if it has always been there i would check with the vet though it could be something serious and even if it isnt they can instruct you on giving you dog some antihistamine
It is a good idea to have the vet check this out.
Are the eye rims fully pigmented?
If not that may be the source of the "always" been like that.
I would guess that it is not allergies since the puppy is 5 months old.
Possible but rare...cause it takes time for antibodies to develop and the average age of when a Maltese presents with food allergies (which this symptom might indicate) is around 3. Possible environmental alegies are the cause but..
Yes check with the vet just to be on the safe side. My guess is she is missing the pigmentation (black) around the eyes.
Not sure Vita if the allergies start only after 3 years old. My late Lhasa started after 2 years old having full blown allergies. But... he had already an ear infection when I got him as a puppy. And I keep wondering if early ear infections are not a sign of an allergy prone dog.