No proven effective way of primary prevention of allergic disease has been found, despite intensive research on environmental and dietary factors assessed, including breastfeeding, maternal diets and dietary restrictions, during pregnancy and lactation.[60] The most promising allergy-preventive alternative is administration of probiotic bacteria. However, giving recommendations on allergy prevention is difficult because the studies have used different probiotic strains and timing.[61] The majority of studies have evaluated eczema as the main outcome rather than food or other allergies. There is a growing body of evidence that primarily L. rhamnosus strains can be effective in preventing eczema. Recent studies show that an effect can be seen until at least 2 years, a good result already, and further some new studies show a longer effect until 5 years. By preventing development of food allergy and eczema, it is hoped that stopping the allergic march would be possible. Combined pre and direct infant postnatal supplementation has demonstrated most consistent effects. Choosing the most effective strains or combination of strains and the mode and length of the supplementation needs to be settled. We still need long-time follow-ups of the rigorous large preferably multicentre studies. We have seen in-vivo immunologic actions related to administration of probiotics, one attractive mechanism relating to low-grade inflammation, but we still have a lack of understanding of the mechanisms behind the allergy-preventive effects afforded by probiotic bacteria. There is also a potential for prebiotics in allergy prevention, but more studies are needed. There is a variation among probiotic studies related to several factors, including probiotic strain/combination of strains, dose, duration, host factors such as allergy risk profile, mode of delivery and type of feeding.