A lot of Toy breeds have the problem of tear staining. Among them is the Papillon.The causes range from small tear ducks (mostly), allergies, stress,blocked tear ducks, caused by infections, or other.
Consult the veterinarian to make sure that there is no infection or other causes which need medical attention.Wipe your Papillons eyes when needed with a soft cloth, or check for those many tear stain removers offered in pet shops, vets, or on line.