Optimal timing for solids introduction - why are the guidelines always changing?

There have been dramatic changes in timing of first exposure to solid foods for children over the last 40 years, ranging from exposure prior to 4 months of age for most infants in the 1960s, to guidelines recommending delaying solids until after 6 months of age introduced in the 1990s. Infant diet, specifically age of weaning and age at introduction of allergenic foods, has long been thought to play a role food allergy. However, controversy surrounding the relationship between timing of introduction of foods and development of food allergy has lead to a plethora of inconsistent infant feeding guidelines both between and within countries. The aims of this article were to discuss the history of changing guidelines for optimal timing of introduction of solids in general and allergenic solids in particular and the evidence (or lack thereof) underpinning recommendations at each of these time-points. We present the current clinical equipoise with regards to recently revised guidelines published almost simultaneously in the UK, US and Australia and argue that guideline modification about timing of introduction (both for high risk infants but also for the general population) will require careful review of emerging literature to provide a true evidence base to inform public health practice such as infant feeding guidelines.