However, they are less susceptible to these effects if they live with at least two pets, namely dogs or cats, in the first year.
Researchers also say breast-feeding and a mother's history of allergies add to the risks of allergy for a child taking antibiotics.
The study's findings are believed to be the first of its kind in the United States that found a link between antibiotics and allergies and asthma in children.
Christine Cole Johnson, Ph.D., the study's lead author and senior research epidemiologist for Henry Ford's Department of Biostatistics & Research Epidemiology, will present the study Sept. 30 at the European Respiratory Society's annual conference in Vienna.
"I'm not suggesting children shouldn't receive antibiotics. But I believe we need to be more prudent in prescribing them for children at such an early age," Dr. Johnson says. "In the past, many of them were prescribed unnecessarily, especially for viral infections like colds and the flu when they would have no effect anyway."
Dr. Johnson theorizes that use of antibiotics may affect the gastrointestinal tract and alter the development of a child's immune system.
The increasing use of antibiotics in children from 1977 to the early 1990s led to what federal health officials called a public health crisis in antibiotic resistance. A national campaign commissioned by the U.S. Centers for Disease Control and Prevention has sought to promote a more judicious approach for prescribing antibiotics for children.
For the Henry Ford study, researchers followed 448 children from birth to seven years. The children were evenly divided by gender.
Data was collected prenatally and at the first four birthdays until the children were 6 and 7 years old, when they underwent a clinical evaluation by a board-certified allergist. The data included information about all prescribed oral antibiotics; blood tests that measure the antibody (immunoglobulin E) that causes allergies; and skin reaction tests that show whether a person is hypersensitive to an allergen. Researchers also collected data on all clinical visits and made home visits to collect environmental samples.
Of the 448 children, 49 percent had received antibiotics in the first six months of life. The most common antibiotic category prescribed was penicillin.
Among the findings:
- By age 7, children given at least one antibiotic in the first six months were 1.5 times more likely to develop allergies than those who did not receive antibiotics. They were 2.5 times more likely to develop asthma.
- By age 7, children given at least one antibiotic in the first six months and who lived with fewer than two pets were 1.7 times more likely to develop allergies, and three times more likely to develop asthma.
- By age 7, children given at least one antibiotic in the first six months and whose mother had a history of allergies were nearly twice as likely to develop allergies.
- By age 7, children given at least one antibiotic in the first six months and who were breast-fed for more than four months were three times more likely to develop allergies. However, breast-feeding did not influence the risk between antibiotics and asthma.
EDITOR'S NOTE: Dr. Johnson is available for interviews in Detroit through Thursday, Sept. 25.