The research, published in JAMA Pediatrics, doesn't prove that antibiotics given to infants cause allergies, only that there's an association between the two. Antibiotics can be lifesaving, so don't hold off on giving your baby antibiotics if your doctor says she needs them, such as for a bacterial infection.
But make sure your baby doesn't take antibiotics unnecessarily, the researchers recommend. Viral infections, such as the common cold, don't respond to antibiotics, so there's no point giving them to your child if she has a virus.
Researchers analyzed the medical records of almost 800,000 children enrolled in a healthcare program for military families between 2001 and 2013. About a fifth of the children were prescribed antibiotics by the time they were 6 months old. These included the following types commonly prescribed to babies: penicillin, penicillin with B-lactamase inhibitor, cephalosporin, sulfonamide, and macrolide.
Later in childhood, the children given antibiotics by 6 months old were more likely than the kids not prescribed antibiotics as babies to be diagnosed with allergies, the study found.
Allergies diagnosed included food allergies, anaphylaxis, asthma, dermatitis, hay fever, and allergic conjunctivitis. Asthma was most strongly associated with the use of antibiotics in infancy, lead researcher Dr. Cade Nylund said.
Also, the more different types of antibiotics prescribed to the children by 6 months, the greater their risk for allergies, the researchers concluded.
Antibiotics interfere with bacteria in the gut. They kill bacteria that cause infections and also kill "good" bacteria that help the body fight disease. The researchers speculated that, in babies, this could leave children more susceptible to allergies.
Additional research is needed to figure out whether antibiotics can actually cause allergies, however. It's possible that the connection can be explained differently. For example, maybe children who develop allergies are more likely as babies to get bacterial infections that require antibiotics.
Speaking with CNN, Dr. Purvi Parikh, an Allergy and Asthma Network spokesperson who was not involved in the research, agreed that parents should be cautious about giving children antibiotics.
"If a child truly needs an antibiotic for a bacterial infection, they should not withhold it due to fear of allergic disease," she said. But "one should not over use antibiotics if not needed – for a virus or a cold – as there may be long-term consequences from overuse."
Confused about when to take antibiotics and when not to? Test your knowledge of what antibiotics won't cure. Also, here are five questions to ask your doctor before giving your baby antibiotics.
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