does anyone know why puppies get the tear stains or eye runs at this age (4 weeks)? My pups are just starting to tear and I've seen it before. They have been wormed and are still in the whelping box on fleece. Mom is still nursing and they started on solids (gruel with yogurt) twice a day about five days ago. It almost seems that it's the solid food causing this since the tearing just started. It does usually go away but I am wondering what causes it and could it be prevented? I thought it was pine shavings but I haven't switched them into the sawdust pen yet.

Lynda, I think you will find that the pineshavings or
any substance that creates airborne dust(beyond the norm) will certainly cause tearing. It could be that the puppies don't like the type of laundry detergent you are using to wash the fleece in(or if you have bleached them, ligering fumes) OR if there is any newspaper in their box with printing(ie. normal newspaper). Would recommend trying some nonprinted newspaper(go directly to your local printing house and purchase OR packing paper in large sheets and adding just a towel or blanket for their sleeping spot. Changing what you wash with in washing machine is pretty easy.
You mentioned it has started with food, well I would change whatever you use as 'gruel' then. I don't use a commerically made food at that age to wean(use Volhard puppy rearing methods) but it might be a good place to start.

To me it's seems to happen when the puppy teeth are coming in. Once the teeth are in the tearing seems to stop. By 8wks of age no more tearing. Just my observation

Where do you live? We are having terrible pollen down South. The mom could be bringing pollen inside to the pups. Most of my dogs are tearing right now due to pollen.

Our ACVO vet told us this can be caused by immature tear ducts. My experience has been that it usually clears up as the pup matures.

Ditto on the immature tear ducts.

GREAT answers and advice. Thanks so much everyone. I do hope it's the tear duct thing, but it does make sense.
The stains look just awful on the little darlings.

My Vet told me the same immature tear ducts. Try taking a cottonball with warm water and working it under the eye from the outside in. wont get rid of staining but does help tear duct.

Likely immature tear ducts. My dog ophthalmologist refers to them as "crocodile tears", since they usually tear when eating.

Slightly off subject, but does anyone have a suggestion for a year-old male who consistently has eye stains? His eyes look perfectly healthy and normal, other than the staining. He's not kept on sawdust either.

What does your ACVO say? I would ask about it during his next CERF exam. It could be a blocked tear duct or something else.