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Every year doctors prescribe millions of antibiotics. But about one-third of the antibiotics prescribed in doctors’ offices are unnecessary, according to a report released earlier this year by the Centers for Disease Control and Prevention.

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Unless an infection is caused by bacteria—which is usually not the case—the drugs will have no effect.

And antibiotics can cause serious side effects, says Laurie Hicks, D.O., a medical epidemiologist and head of the CDC’s program Get Smart: Know When Antibiotics Work. These can include allergic reactions as well as an infection called C. difficile, which can cause severe—and sometimes deadly—diarrhea.

Plus, she says, the more bacteria are exposed to antibiotics, the less likely they are to respond to the drugs. “You increase your risk of developing an antibiotic-resistant infection the more antibiotics that you take,” Hicks notes.

Doctors know that, but they often prescribe antibiotics anyway, in part because patients expect it. 

For U.S. Antibiotics Awareness Week, the CDC is encouraging people to learn about when antibiotics are needed and when they’re not. Here are six conditions where it’s wise to question the use of antibiotics.

1. Respiratory Infections

Colds, the flu, and most other respiratory infections are caused by viruses, which generally can’t be wiped out by antibiotics. Bronchitis is usually caused by a virus or an irritant in the air, such as cigarette smoke. Most sore throats are viral, too.

For these viral infections, skip the antibiotics and ease symptoms by drinking plenty of liquids, breathing moist air, gargling with salt water, and taking acetaminophen (Tylenol and generic) or ibuprofen (Advil and generic).

About one in 10 sore throats are due to strep, a bacterial infection that can be treated with antibiotics, Hicks says. So talk to your doctor if you or your child show signs of strep, such as a sore throat that comes on suddenly, accompanied by a fever but without a cough, swollen lymph nodes in the front of the neck, swollen tonsils, or tiny red dots on the roof of the mouth. He or she can do a rapid strep test to diagnose the condition.

2. Sinus Infections

Sinusitis, which can prompt a stuffy or runny nose and facial pain, is almost always caused by a virus. Even when bacteria are the cause, these infections usually clear up on their own in about a week.

To loosen mucus and help it drain, drink warm liquids; breathe warm, moist air; and keep your head propped up when you lie down.

Consider antibiotics only if you’re still sick after 10 days, if you get better and then worse again, or if you have a high fever and thick, colored mucus for three or more days in a row.

3. Ear Infections

Most ear infections improve on their own in two or three days, especially in children ages 2 or older.

Give your child over-the-counter pain relievers for a few days, and avoid antibiotics. Go to a doctor if symptoms aren’t better in two to three days or if they worsen.

Get antibiotics right away for babies 6 months or younger, for children 6 months to 2 years old who are experiencing moderate to severe ear pain, and for children 2 years or older with severe pain, according to the American Academy of Family Physicians.

4. Pink Eye

Pink eye (conjunctivitis) is usually caused by a virus or allergy, so antibiotics won’t help. Even bacterial pink eye usually goes away on its own within 10 days.

Soothe pink-eye symptoms with a clean, cool, wet compress. Pink eye resulting from allergies can be helped with antihistamine eye drops.

Consider antibiotics for bacterial pink eye if you have a weak immune system, if the condition doesn’t improve in a week without treatment, or if the eye is very swollen or painful or develops a thick, puslike discharge.

5. Urinary Tract Infections in Older People

Antibiotics are useful in treating urinary tract infections (UTI). But sometimes older adults are treated for a UTI after a routine urine test reveals bacteria—even if they’re not experiencing symptoms.

“It is not uncommon in older adults to find that bacteria are living in the bladder but not necessarily causing an infection,” Hicks says.

Consider antibiotics only when UTI symptoms, such as pain or burning during urination or a strong urge to go often, are present as well.

6. Eczema

Doctors may try to control eczema, which causes dry, itchy, red skin, with antibiotics. But antibiotics won’t help with itching and redness.

To ease eczema, moisturize your skin regularly and avoid triggers, which vary from person to person. Ask your doctor about a medicated cream or ointment to relieve itching and swelling.

Consider antibiotics only if you show signs of a bacterial infection, such as bumps full of pus, honey-colored crusting, very red or warm skin, or a fever.