Prevention of allergy. Dietary intervention during pregnancy and the firstyear of life.

Primary prevention of allergy before birth and during the first year of lif e can be directed towards a target population with a high risk of allerqy, or the general population when health authorities decide that a large-scale prevention campaign should be conducted. Despite several prospective studi es, some of which are still underway, prevention of allergy raises difficul t problems. The combination of dietary intervention in the mother (during p regnancy and breastfeeding) and in the child (for the first 2 years of life ), and strict control of the household allergenic environment appears to gi ve good results in neonates at high risk of allergy. A consensus has been r eached concerning the simple measures to be proposed to couples with a high risk of allergy: effective cessation of smoking, encourage breastfeeding, delay the introduction of solids, and maintaining the child's household env ironment as minimally "allergenic" as possible, constitute four acceptable proposals, recommended by basic health education. Primary prevention of all ergy in the general population raises far more complex problems. Thorough c ost-efficacy studies are essential. In every case, primary prevention must take into account the efficacy of secondary prevention and the possibilitie s of pharmacological control of the symptoms. Prevention programmes can hav e harmful effects (dietary imbalances during exclusion diets in mothers, ps ychological difficulties related to complex programmes that are difficult t o maintain).