To remove porphyrins from the dog, use contact lens cleaner. Yes, you heard me well! Contact lens cleaners contain boric acid that can help oxidize iron present on porphyrins which helps lighten them.
Dampen a cotton ball in a contact lens cleaning solution. Rub the dampened cotton ball on the tear stain.
Note: This should be done once or twice daily, and make sure the solution doesn’t get into your pet’s eye.