Children exposed to antibiotics during their first year of life may have increased risk of contracting childhood asthma. Studies found that exposure to one course of antibiotics can double the risk for developing asthma. The risk increases with every course of antibiotics taken. Scientists mentioned that no definite link was established between antibiotics and asthma, but the fact that they found an association between antibiotic use and the subsequent development of asthma is in itself a fairly substantial message. But I don't think it's by any means conclusive. "It appears to be an association, but we need further study," said Carlo Marra, a professor of pharmaceutical sciences at the University of British Columbia and author of the study. About 18 million Americans of all ages have asthma. The study analyzed 7 prior studies conducted between 1999 and 2004. They included more than 12,000 children under 1 year who took antibiotics. More than 1,800 of these went on developing asthma. Analysis of other 5 studies considered 27,000 children out of which 3,400 contracted asthma. Children who received more antibiotics had a higher risk of developing asthma. The studies which considered past medical research indicated an antibiotic-asthma connection, but are sometimes inaccurate because they rely on the parents' recollection. Dr. Glenn Flores, a professor at the Medical College of Wisconsin declared: "There's no known pathological basis that would associate antibiotic use with childhood asthma. Antibiotic use itself could be a marker for a child who has more childhood illnesses in the first place, so it looks like the antibiotics have a link to asthma when [in fact] it's just a correlation with a greater incidence for disease with that particular child."