Natural tolerance development
In 2015, the groundbreaking British study 'Learning about Peanut Allergy (LEAP)' demonstrated that regular consumption of peanut products until the age of five years (4) reduced the risk of peanut allergy by 60 % compared to avoiding peanut products (5). The study involved over 620 infants from 4 months of age with severe eczema and/or an egg allergy, who thus had a high risk of developing a peanut allergy. The findings documented for the first time the significance of natural tolerance development through exposure and sparked changes in several infant nutrition guidelines.
Two large population-based studies have examined whether food allergens introduced from three months of age can prevent food allergies (6, 7); the British study 'Enquiring about Tolerance' (EAT), which included over 1300 children (6), and the Scandinavian study 'Preventing Atopic Dermatitis and ALLergies (PreventADALL), with around 2400 children (7). In the EAT study, infants were randomised to receive specific amounts of peanut products, boiled egg, cow's milk, sesame, wheat and white fish weekly, and these children were compared to a control group that followed standard advice on exclusive breastfeeding until six months. Among the roughly 30 % who adhered to the protocol, the risk of developing an allergy was significantly lower (2.4 % vs 5.5 %) (6). In the PreventADALL study, the children were randomised to receive a taste of finely ground peanut butter, cow's milk, wheat and soft scrambled eggs at least four days per week from three months of age until at least six months, in addition to breastfeeding, while the control group was advised to follow national guidelines (7). Children randomised to early introduction of solid foods had a 60 % lower risk of an allergy to at least one of the foods at the age of three years compared to the control group (1.1 % vs 2.6 %) (7).
A large meta-analysis, which included data from PreventADALL and EAT, documented that food allergies can be prevented through early introduction of foods (2). This analysis found strong evidence that the risk of egg and peanut allergies was significantly reduced by introducing these foods before six months of age (2). Furthermore, it found moderate evidence that introducing multiple foodstuffs reduces the risk of an allergy to at least one of these, while no preventive effect was associated with cow's milk.