Peanut allergy is the main cause of anaphylaxis and affects approximately 2%.1 In oral immunotherapy (OIT), allergic individuals start eating very low doses of the allergen and gradually increase it up to a maintenance dose. The goal is to induce desensitization or, preferably, tolerance to the allergen. In a study of 496 children (4–17 years) receiving peanut OIT, 67% achieved desensitization for ≥600 mg peanut protein after 1 year of treatment with 300 mg peanut protein/day.2

Mild allergic reactions are common adverse events during OIT and anaphylaxis sometimes occurs. A study of OIT in younger children (9–36 months) indicates that OIT might be more successful and safer in younger children. No anaphylaxis was observed, and 85% tolerated peanuts at a challenge 4 weeks after discontinuing OIT.3 It seems that intervention early in life may affect the immune system towards development of tolerance. Studies about immunological markers in blood and faeces predicting or correlating the outcome of OIT treatment in young children are sparse.4, 5 How the intestinal microbiome changes over time in young children with or without OIT is to a large part unknown.

In this Letter, we report the protocol of a clinical open-labelled randomized controlled trial (RCT) with peanut OIT treatment or avoidance (ratio 2:1) in peanut-allergic children aged 1–3 years. The overall aim is to study whether oral immunotherapy with a low dose and slow up-dosing strategy in 50 peanut-allergic young children (1–3 years) is safe and effective.