Asthma and allergic diseases generally start early in life and persist throughout life but, for reasons we do not yet understand, they sometimes appear later Prevention, early diagnosis and treatment of these major chronic respiratory diseases is a recognized priority for EU public health policy and for the United Nations. As factors favoring allergy (rapid urbanization, pollution, climate change and infections) are not expected to change in the foreseeable future, it is crucial to develop, strengthen and optimize prevention and treatment. We have developed tools to control asthma but are still unable to prevent children from developing asthma and allergic diseases. This article examines what works and what does not, and analyzes the "missing links" between the creation and effective implementation of a prevention program, otherwise known as the implementation gap.