Research published in the American Journal of Epidemiology shows that children who receive antibiotics in the first six months of their lives are 52% more likely to develop asthma by six years of age. Previous studies with similar results may have been biased because antibiotics are used to treat respiratory tract infections (RTIs) that may actually have been early symptoms of asthma. The new study eliminated this bias and concluded that antibiotic use increased the risk of developing asthma in children who had not had any RTIs.

The study found the effect of antibiotic use is also different in children who are genetically pre-disposed to asthma, and found that after antibiotic use children without asthmatic parents had a stronger risk of developing asthma.

Lead researcher Michael B. Bracken, professor of epidemiology at the Yale School of Public Health says the antibiotic use and increased asthma and allergy risk relate to the hygiene hypothesis, which may explain why asthma rates have increased in developed countries.

Early exposure to antibiotics may suppress or cause imbalance in the developing immune system and produce a reduced anti-allergic response. The researchers say that exposure to dirt and microbes in the intestinal tract early on may be necessary for a mature and balanced immune system. A third of US infants are exposed to antibiotics in the first six months of life, and antibiotics are prescribed for RTIs even though these are mostly viral diseases that will not respond to antibiotics.

These findings should encourage physicians to avoid unnecessary antibiotic use.

Source: American Journal of Epidemiology

First Published in Janury 2011

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