Dear Dr. Fox: I have read that giving yeast to a pet keeps roundworms out of the pet’s system.

Does this work on dogs? If so, what type of yeast is advisable? And should it be mixed into the pet’s daily meal? — Mrs. W.P.

Dear Mrs. W.P.: Brewer’s yeast or nutritional yeast is of little use in keeping roundworms out of a pet’s system. It is used as a nutritional supplement, skin conditioner and flea preventative.

The best treatment for roundworms is worming medicine from your veterinarian.

Yeast does sometimes help keep fleas away.

Dear Dr. Fox: A reddish-brown discharge continually seeps from the corners of my white toy poodle’s eyes. It runs down his face and dries to a sticky goo that will not come off when I wash him.

I have tried a product that is supposed to combat this condition, but it didn’t work. — P.A.W.

Dear P.A.W.: First, have the veterinarian check your dog for any eye abnormality that could cause excess tearing. Wipe your dog’s face every third or fourth day with diluted hydrogen peroxide, but be sure not to get it in his eyes.

Although some of the pigment in your dog’s tears is a natural secretion, some could be coming from pet food dye. So try your dog on a natural pet food that’s free of dyes.

Dear Dr. Fox: Recently, we had to put our beautiful black cocker spaniel to sleep because of chronic ear infections. We had fought them for two years with antibiotics, eardrops, peroxide cleansing, etc., only to have the infections recur.

Putting her to sleep was the most humane thing to do, as in the end, her equilibrium was off, and she could barely raise her front paws.

We are heart-broken and would love to have another cocker, eventually — they are such good dogs. Is there anything we could have done to prevent the problem? She was only 5 years old. — R.S.

Dear R.S.: Cockers are very prone to ear problems. They have been bred to have heavy, pendulous ears, but those ears prevent the ear canals from “breathing.”

Some spaniel breeds, such as the Springer and English cocker, don’t have such heavy ears as the American cocker spaniel. You might consider getting one of these to avoid future ear problems.

With chronic ear disease, plastic surgery to open up the ear canal is often the only remedy, and then it’s no guarantee of a permanent cure.

—- The Animal Doctor appears every Monday. Write to Michael Fox, United Features Syndicate, 200 Park Ave., New York, N.Y. 10166.