Development of atopic disease seems to depend on both genetic factors and exposure to several environmental factors. At present ther is evidence that the mode of early infant feeding influences the development of food allergy, whereas daily exposure to inhalant allergens and daily exposure to tobacco smoke is found to be associated with an increased risk of recurrent wheezing/asthma and inhalant allergy. In infants with atopic predisposition (first-degree relatives), exclusively breastfeeding > or = four months is found associated with a significant reduction of the cumulative prevalence of cow's milk allergy/intolerance (CMA/CMI) during the first 1-2 years of age. When breastmilk is insufficient or lacking a substitute formula is needed. Several recent prospective studies show a preventative effect of extensively hydrolysed formula (eHF) in combination with avoidance of cow's milk proteins and solid foods during > or = 4 months in high-risk infants on the cumulative prevalence of food allergy and atopic dermatitis during the first 2-4 years of life. Partially hydrolysed formulas (pHF) may be effective in allergy prevention, but due to drawbacks of study design and lack of documentation pHF cannot be recommended at present. The results of studies comparing the preventive effect of eHF and pHF are awaited. The protective effect on the development of cow's milk allergy is a real prevention and not only a postponement of the onset of symptoms. No studies have demonstrated a preventive effect of dietary measures as regards asthma/inhalant allergy, at present until the age of four years. As no studies concerning the preventive effect of avoidance of milk and other foods after the age of 4-6 months of life have been performed, recommendation of preventive elimination diets beyond this age is empirically based. In order to reduce the costs, to minimize the risk of stigmatisation and the risk of malnutrition it is important to avoid unnecessary restrictive and prolonged diets. A diet period of 4-6 months seems sufficient in most infants. At present eHF are recommended for avoidance of cow's milk. Some high risk infants may benefit from maternal diet during lactation, but there is no documented beneficial effect of maternal diet during pregnancy.