A: Mimi, although greenish mucus looks yucky, it is usually not a sign of a bacterial infection and does not usually need treatment with antibiotics.

The common cold—the most common illness in children—is caused by a virus infection. Once the virus invades the nose, the body’s defenses start to fight against it—this is what causes the symptoms of the cold. The symptoms typically start with nasal congestion, runny nose, and sometimes a low-grade fever. The runny nose usually starts out with lots of clear mucus. When the body’s immune defenses send white blood cells to fight off the virus, it makes the mucus thicker and turn whitish, yellowish or greenish in color. Rather than being a bad sign, the greenish mucus is usually a good sign that the body’s defenses are strong and the cold is ending, usually by 7-14 days.

When your child has a cold, make sure you give him rest, fluids, and tender loving care. But don’t ask your doctor for antibiotics. There are several important reasons why:

1. The cold will get better on its own.
2. Antibiotics won’t help your child get better. They only work against bacterial infections, not viral infections like colds.
3. Taking antibiotics when they’re not necessary can make bacteria resistant to the antibiotics, so the antibiotics are no longer effective when really needed.

Rarely, a cold may not get better on its own and can lead to a bacterial infection, such as an ear infection, sinus infection or bronchitis. If your child continues to have green mucus after 14 days and develops a fever, severe headache, earache or cough, call your doctor to check your child and see whether treatment may be needed.

For more information, see the Centers for Disease Control fact sheet “Get Smart: Know When Antibiotics Work” at
www.cdc.gov/drugresistance/community//files/CDC_parents_brochure1.pdf .