What Parents Should Know About Babies and Antibiotics

Learn when babies should have antibiotics, when they shouldn't, and what side effects to look out for.

sick baby
Photo: Alexandra Grablewski

When your little one is sick, it's natural to want your pediatrician to prescribe something that will make them feel better fast, and many parents jump right into requesting antibiotics. But depending on your baby's symptoms and illness, antibiotics (which are medications that fight bacteria) are not always the right choice.

"Antibiotics are only effective against bacteria, which means they're useless against viral ailments like the flu and colds," explains Iona Munjal, M.D., director of the Pediatric Antimicrobial Stewardship Program at The Children's Hospital at Montefiore Medical Center in Bronx, New York. And prescribing antibiotics when they are not needed can do more harm than good, according to the American Academy of Pediatrics (AAP).

We talked to the experts to learn more about how and when antibiotics can help a baby, and when they can't.

When Do Babies Need Antibiotics?

In general, experts say that babies only need antibiotics when what's making them sick is a bacterial infection. The following are the most common childhood ailments for which doctors will sometimes prescribe antibiotics.

High fever

"A fever indicates that the body's immune system is fighting off germs," says Dr. Munjal. This is a good thing, but temperatures that spike too high (100.4°F for babies younger than 3 months and 102°F for ages 3 to 12 months) may signal a more serious bacterial infection—though this isn't always the case, as high fevers might also have viral causes. Visit your doctor if you're concerned your little one has a bacterial infection that might require antibiotics.


It's difficult to determine whether the cause of pneumonia is viral (perhaps due to an upper respiratory infection) or bacterial. Symptoms of pneumonia usually start with fever, coughing, shortness of breath, and/or vomiting.

Because infants have a higher risk of complications from pneumonia, including breathing difficulties, pediatricians often prescribe antibiotics such as amoxicillin, ampicillin, and penicillin for pneumonia, even if they aren't positive that it's a bacterial infection.

Pertussis (whooping cough)

Antibiotics are most effective when started within the first week or two of pertussis, when early symptoms include a mild cough or fever and before the signature whooping cough begins. It's important to note, however, that while antibiotics can stop the spread of the infection, they won't prevent or treat the characteristic cough, according to the AAP.

Azithromycin is typically the first choice for treating pertussis but other options include clarithromycin and erythromycin. The best way to prevent whooping cough is to ensure your baby is caught up on recommended vaccinations and to encourage any caregivers for your baby to get vaccinated as well.

Ear infections

If your older child has an ear infection, your doctor may wait 7 to 14 days to see if it clears up without treatment. About half of all ear infections resolve on their own without antibiotics, and many ear infections are actually viral (meaning an antibiotic wouldn't treat the infection anyway).

But infants are the exception to this wait-and-see approach: "A baby can't tell you how much pain he's in or if he's feeling worse, which is why most pediatricians prescribe an antibiotic like amoxicillin," says Allison Bartlett, M.D., a pediatric infectious disease specialist at La Rabida Children's Hospital in Chicago.

Signs your baby may have an ear infection include ear tugging or pulling, excessive irritability or crying, sleeping difficulties, and high fever.

Urinary tract infections (UTIs)

Urinary tract infections occur when fecal or other bacteria enter the bladder or kidneys. Fever is typically the only sign of a UTI in an infant, but some other symptoms can include irritability, vomiting, or diarrhea.

"A urine culture can confirm the diagnosis and identify which bacteria are causing the infection," says Dr. Bartlett. "This helps the doctor choose the best antibiotic to target those specific bacteria."

Other bacterial infections

Infants rarely develop strep throat (which involves symptoms of fever, sore throat, and trouble swallowing) or sinus infections (or excessive nasal congestion along with a fever or cough) that require antibiotics, but both are possible.

Is It Safe to Give Antibiotics to Infants?

Antibiotics are generally very safe medications for children. But like all medications, they can cause side effects or other problems.

Allergic reactions

Only a small percentage of children have an allergy to antibiotics. For instance, about 10% of children in the U.S. are allergic to penicillin, a common antibiotic. Signs of an allergic reaction to penicillin or other antibiotics could include hives or red, swollen, itchy welts.

"Compared with hives, a rash is much less severe and is more likely related to a viral infection, not a medication response," says Dr. Munjal. Still, you should let your doctor know if your baby develops a rash while taking antibiotics. "Treating the rash with an allergy medication like Benadryl usually isn't necessary," says Dr. Munjal.

Side effects

About 1 in 10 children experience side effects from taking antibiotics, according to the AAP. The most common are diarrhea, nausea, and stomach pain. "In addition to targeting bad bacteria, antibiotics kill off healthy bacteria in the gut. This can lead to stomach upset or diarrhea," says Dr. Munjal.

You could talk to your doctor about some ways to help restore the bacteria in your child's stomach, such as giving probiotics, which are "good" bacteria.

Antibiotic resistance

As more antibiotics are used through the years, bacteria evolve making these medications less effective. This is known as antibiotic resistance, and it's a key reason that doctors are very cautious about prescribing antibiotics only when absolutely necessary.

How Quickly Do Antibiotics Start to Work?

Most children start to feel better within 48 to 72 hours of starting treatment, but it is important to give the medicine for the prescribed length of time even if your child seems better, says the AAP. Stopping medication early can cause the infection to return.

"A doctor may then need to prescribe a stronger antibiotic because the bacteria has built up resistance to the first medication, making the germs harder to kill," says Dr. Bartlett.

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