Your dog's tear stains are caused by liquid secretion from his eyes, which gradually permeates the fur around his eyelids. While most dogs have at least some tear stains around their eyes, the problem is much more visible on dogs with white or light-colored fur. Many dog owners are concerned with the cosmetic effect that the stains have on their dog, but these moist patches of fur can also foster the growth of disease-causing bacteria.
Examine your dog's eyes several times each day. Note the moistness of his eyes and how big the tear-stained area is. As you watch your dog, look for changes in the severity of the staining problem. Excessive tear stains may be the result of external factors, including an immune system reaction to a particular type of food or allergen. If your dog's eyes are wetter than usual during a particular season, or when eating a certain type of food, it may be an indication that allergies are the problem. Some dogs are genetically predisposed to generating tear stains, so there is a possibility the condition is purely physiological.
Mix a teaspoon of cider vinegar with your dog's water each day. This increases the pH of the water, which helps combat the growth of microorganisms that make the tear stain problem worse. You can also take your dog to a veterinarian and ask if an antibiotic is necessary. The bacteria that exacerbate tear stains aren't particularly dangerous, but they do cause the stained fur to emit a foul odor.
Moisten a clean cloth with room temperature, or slightly warmer, water. You can also use a weak saline solution or lemon juice mixture instead of water. Wring the cloth out before wiping your dog's eyes. Hold your dog's head still and gently wipe the stained area around his eyes. Avoid the eye itself, as saline and lemon solutions can sting your pet's eyes.
Apply an approved commercially available tearstain removal product or make one yourself from basic ingredients. Mix equal amounts of milk of magnesia and peroxide in a bowl, then stir in small amounts of cornstarch until the solution becomes a paste. The solution should be thick enough so that it does not run or drip. Apply the solution to the stained fur around your dog's eyes with your hands. Rub and massage it into the fur, so that it coats the hair all the way to the roots. Let the paste dry for several hours, then rinse it out with warm water or wipe it with a wet cloth.