T he common cold is caused by any of more than 300 viruses. Protect yourself by observing the following rules...

Stop stressing yourself out. Pushing yourself too hard depresses the immune system. When your defenses are down, you are more vulnerable to infection by a cold virus.

Go to sleep at a reasonable hour. A fully rested body is better able to resist infection. Know your limits--physically and emotionally--and try not to exceed them.

Wash your hands after using staplers, copiers, fax machines and any other common office equipment, especially when any of your coworkers have colds.

Viruses can live on hard surfaces for hours, even days. In fact, you can become infected with a cold virus on an airplane--not from the recirculating air, but from touching the lavatory door. If you can't get to a sink, use an alcohol-based antibacterial gel.

Eat wisely. A healthful diet is especially important to keep your immune system strong. The basics--no junk food, lots of fruits and vegetables and plenty of noncaffeinated liquids.

Some doctors recommend 1,000 mg to 2,000 mg of vitamin C per day to strengthen your defenses against cold viruses. This seems to reduce the severity of cold symptoms.

WHEN YOU FEEL A COLD COMING ON

Take echinacea. While recent research on hundreds of people found that echinacea was no more effective than a placebo, in my experience it is a very good placebo.

Although the effectiveness of this herb is controversial, many doctors, especially in Europe, believe it can shorten the duration of a cold and lessen the severity of the symptoms.

I prefer the tincture. Take 15 to 20 drops diluted in one-quarter of a glass of water, four times a day. Continue this dosage for about two weeks, if necessary... then stop.

Important: Not for everyone. Anyone with immune system disorders, such as lupus or scleroderma, should not take echinacea. Check with your doctor.

TREATING A COLD

Drink hot fluids. The best liquid for a cold is hot chicken soup. It works more effectively than most other soups--but no one knows exactly why.

Hot tea and steaming lemon-flavored water also keep nasal passages open.

A vaporizer--hot or cold--can provide the same steam-clearing effect in your nasal passages.

Take an antihistamine to relieve a stuffy nose. While antihistamines won't cure a runny nose, their drying effect may make you feel better. They are especially good when there is an allergic component to the cold.

Beware: Men with prostate problems may experience difficulty urinating and should avoid antihistamines.

Nasal decongestants that are sold over-the-counter or nasal spray can also relieve stuffy nose symptoms.

Treat coughs with the right cough medicine.

If you have a cough that is producing phlegm, choose medicine with the ingredient guaifenesin. It loosens the mucus that is causing you to cough.

If you have a dry, irritating cough that doesn't produce mucus, you may wish to suppress it during the night so you can sleep. Choose a cough medicine with the codeine-like ingredient dextromethorphan.

Avoid antibiotics--in most cases. If, however, your cold turns into bronchitis or you have a persistent fever or green sputum, your doctor may then prescribe antibiotics.