Discolored stains around puppies' eyes are caused by mucus or constant tearing. Teething, eye infections, genetics, improperly formed tear ducts, allergies, and reactions to impurities in food and water can all contribute to the problem. Removing stains is fairly easy; diligence in keeping the area clean will prohibit their return.
Visit a groomer to have the hair around your puppy's eyes trimmed, and make regular visits to keep it short. Longer hair will hold tears or mucus, which creates staining. Shorter hair is easier to clean and keep clean.
Wipe the hair under your puppy's eyes daily—several times a day if his eyes are continually watery. Wet a cotton ball or soft cloth with warm water to wipe tears and mucus from the hair. This will clean current stains and prevent new ones from forming.
Wash stains with contact lens saline solution. Wet a cotton ball or swab with saline solution and rub it gently into the stain. Wipe with a clean cloth and repeat. Commercial eye and stain washes for dogs contain saline; the small amount of boric acid in the contact solution also lightens the stains. Use daily to prohibit the return of stains.