Infants receiving acid suppressive medications are more than twice as likely to develop food allergies later in life, US researchers say.Findings from a large retrospective study, analysing data from almost 800,000 children, showed that being prescribed either an H2 receptor antagonist or a proton pump inhibitor in the first six months more than doubled the risk of developing a food allergy (hazard ratios of 2.18 and 2.59 respectively) when they got older.Similarly, the use of these medications was also found to associated with an increased risk of other allergies as well, including medication allergy (HR 1.70 and 1.84), anaphylaxis (HR 1.50 and 1.45) and, to a lesser extent, allergic rhinitis and asthma.As part of the same study, the researchers also looked at antibiotics in the first six months and, perhaps unsurprisingly found a link between this type of medication and developing an allergic condition. In the case of antibiotics, children were more likely to develop allergic respiratory conditions such as asthma and allergic rhinitis than food allergies.The findings have biological plausibility, the researchers said in JAMA.Acid suppressive medications inhibit the breakdown of ingested protein which, in turn facilitates IgE antibody production increasing the sensitivity to ingested antigens. The medications also, by definition, interfere with histamine which researchers now believe has a greater role in modulating immune system functioning than previously thought.The association between increased allergy and antibiotics, on the other hand supports findings from previous studies, and is thought to be related to the effect of the antibiotics on the gut bacteria or microbiome. It is one of a number of reasons why there has been growing pressure on clinicians to try to avoid prescribing antibiotics to infants.“While there has been increasing recognition of the potential risks of antibiotic use during infancy, H2 [receptor antagonists] and PPIs are considered to be generally safe and are commonly prescribed for children younger than a year,” the study authors say.Among the almost 800,000 children included in the study, 7.6% had been prescribed a H2 receptor antagonist in infancy and 1.7% had had a PPI.The researchers did concede that a limitation of this study could be ‘the potential bias from reverse causality’. Namely an infant’s symptoms of a food allergy could have originally been misdiagnosed as gastro-oesophageal reflux necessitating acid suppression, or early symptoms of asthma could have mistakenly been thought to be an indicator of a bacterial respiratory infection.However, the authors say, this is unlikely to be the whole story. Such scenarios cannot explain the increased rates of anaphylaxis or urticaria or medication allergy. And many food allergies don’t develop until well after the first six months so it would be unlikely that allergy would have caused the symptoms experienced by an infant.All in all, best practice, according to these researchers is to minimise the use of acid suppressive medications and antibiotics in children, particularly in children less than six months old.“This study provides further impetus that antibiotics and anti-suppressive medications should be used during infancy only in situations of clear clinical benefit,” they concluded.