You are not aware of them, but tears are always present on the surface of your pet's eyes. They act as a lubricating fluid, keeping the eyes moist and protecting them from dirt and scratches. They also contain enzymes that help to prevent the growth of bacteria.

Sometimes the tear ducts open wide, producing torrents of water. This usually occurs when something lodges in the eye and irritates the surface. Copious tears are the body's attempt to flush it out. "When tearing comes on suddenly, the tears are clear, and just one eye is affected, you can be pretty sure that the cause is a foreign object," says Nancy Willerton, D.V.M., a veterinarian in private practice in Denver.

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Dogs such as basset hounds, bloodhounds, and Newfoundlands are especially prone to problems because they have a large space between the eyelids and the surface of the eye, which allows grit to get inside.

Watering sometimes occurs if the conjunctiva, a thin layer of tissue covering the inside of the eyelids, gets irritated. A speck of grass or dust can irritate the conjuctiva, sometimes causing the eye to water for days. Too much sun or wind -- from riding in the car with the windows open, for example -- can also cause the conjunctiva to get red and inflamed.

A more serious cause of watery eyes is when the cornea, the surface of the eye, gets scratched. "Corneal scratches are painful, and your pet may squint to shut out painful light," says Dr. Willerton.

When both eyes are tearing and the liquid is clear, there is a good chance that your pet has allergies that are similar to hay fever in humans. "If the tearing starts at a change of season, you will have good reason to suspect an allergy," says Merry Crimi, D.V.M., a veterinarian in private practice in Milwaukie, Oregon. Other signs of allergies include red eyes and itchy ears, she adds.

Pets with glaucoma, a serious condition in which fluids accumulate inside the eye, will often have watery eyes. The eyes may also be dilated as well, causing the pet to squint to block out the excess light that his wide-open pupils are letting in.

In cats, watery eyes may be caused by viral infections such as feline respiratory disease. If the infection is serious, watery eyes may be accompanied by other symptoms, like sneezing, drooling, or a loss of appetite. In addition, the eye discharge may change from clear to yellow, sticky, and puslike.

Watery eyes aren't always a problem. Certain short-faced breeds like miniature poodles and Persian cats have bulgy eyes, and they need the extra tears to keep their eyes moist. In fact, some breeds only appear to produce a lot of tears. Because of the way their heads are constructed, the tears may run down their faces instead of along the tear canals, making the moisture more visible.

See Your Vet If...

• Your pet is squinting
  
• He has been riding with his head out the car window
  
• Your pet has bloodshot eyes and itchy ears
  
• Your pet won't quit scratching or pawing his eyes
  
• His eyes have turned blue, gray, or cloudy, or he is having trouble getting around
  
• His eyes are frequently bloodshot or dry
  
• There has been a watery or discolored discharge from the eyes for 48 hours or more
  
• Your pet's eyes are bulging
  
• The eyelids are swollen or unable to close
  
• There is a growth on the eye or eyelid
  
• One or both pupils are dilated, or they don't respond to light
  
• Your pet seems very sensitive to light
  
• The eyes are droopy or sunken
  
• The third eyelids are covering the lower parts of the eyes
  
• His eyes are continually moving back and forth
  
• Blood or tiny blood vessels are visible in the center (not the whites) of his eyes
  
• His eyelid appears to be turned inward or outward
  

Next Steps:

• What you can do for your pet
  
• What your vet can do
  
• Find out other causes of watery eyes

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