If you’re prone to bronchitis or pneumonia or have asthma, you may freak out any time someone near you coughs or sneezes, as viral droplets waft through the air, landing on pens, doorknobs, your clothes—or in your eyes or nose. You may pull out all the stops to prevent getting sick, but what if, despite your best efforts, you get snagged by a head cold? Here’s how to keep that cold from taking over your lungs.

KEEP A COLD OUT OF YOUR CHEST

There are two ways that a head cold can burrow into your lungs, according to Richard Firshein, DO, director of the Firshein Center for Integrative Medicine in New York City. One is just that the same virus causing the head cold moves from the nose and throat to the lungs. The other is that another infection—usually bacterial—takes advantage of the weakened immune system. No matter what, you can avoid this one-two punch.

As soon as you feel the first symptoms of a cold coming on, Dr. Firshein recommends taking vitamin C and zinc. “This regimen is not a cure-all, but it will help shorten the duration of the problem, and, for many people, it will keep the immune system healthy enough to get through the head cold without it turning into a chest cold,” he said.

Dr. Firshein recommends at least 500 milligrams (mg) per day of vitamin C, taken in a split dose (250 mg twice per day) for three to five days. Don’t take more than 1,500 mg daily or you will risk side effects, such as painful kidney stones and soft stools or full-blown diarrhea. As for zinc, whether in lozenge or tablet form, Dr. Firshein recommends a dosage of 10 mg to 25 mg twice a day until symptoms clear. Be aware, though, that zinc lozenges and tablets can cause upset stomach or a metallic taste.

“Most people will do fine with vitamin C and zinc,” Dr. Firshein said, “but some people, such as the elderly and those with certain health conditions such as asthma or heart disease, may need to add other supplements to fortify their immune systems.” Dr. Firshein’s go-to supplements for people who need an extra boost include…

Echinacea. This herb, from the daisy family, has antioxidant and antiviral properties and fortifies the immune system against bacterial attack. In all, it can reduce the length and severity of colds. Dr. Firshein prefers a liquid extract dispensed by dropper and recommends formulations marketed by Herb Pharm and Gaia.

Cordyceps. Cordyceps is a potent immune-strengthening nutrient derived from a fungus that grows inside caterpillars that live high in the Himalayan mountains. It’s expensive…and natural cordyceps supplements can be hard to find. Dr. Firshein recommends these brands—Host Defense and Jarrow Formulas. He suggests a starting dosage of two 500-mg capsules once per day.

EXTRA DEFENSE FOR ASTHMATICS

If you have asthma, you especially want to guard against chest colds. The combination of swelling and mucus production from a chest cold makes breathing even more difficult. It can also bring on dangerous—and deadly—constriction of the airways (bronchospasms).

“People with asthma have to be more vigilant,” said Dr. Firshein. “They should use all of the vitamins and supplements mentioned above and fortify their immune systems with N-acetylcysteine (NAC) and magnesium.”

NAC is an antioxidant that can dissolve and loosen mucus, so it will help clear the airways. Dr. Firshein recommends a dosage of 250 mg twice a day. Magnesium is a natural bronchodilator, so it will also help open up the airways. Again, Dr. Firshein recommends 250 mg twice a day.

As a final word to the wise, Dr. Firshein urges that you see a doctor if your symptoms worsen instead of improve. Also see your doctor if an asthma attack occurs during a cold, if a bad cough doesn’t go away after other cold symptoms resolve or if your temperature climbs over 99.4°F.