Open label study with peanut oral immunotherapy (OIT). Peanut allergic children aged 1-3 years of age will be randomized 2:1 to:

1. Peanut OIT with slow up-dosing (40-60 weeks) up to a maintenance dose of 285 mg daily oral peanut protein or
2. Control group with peanut allergic children who do not undergo OIT.
3. In addition, a group of healthy children without allergic diseases will be included in the study.

The primary outcome is tolerance to at least 750 mg peanut protein at a challenge after 3 years and sustained unresponsiveness (i.e. tolerance) to 750 mg peanut protein after 3 years of OIT followed by 4-6 weeks of avoidance.

Efficacy and safety will be compared between group 1 and 2. Group 3 is a control group for analyses of immunological markers.

Problem: Today there is no clinically available treatment for peanut allergy. Oral Immunotherapy (OIT) studies have shown promising results, particularly in younger children (<4 years).

Intervention: Peanut OIT in children aged 1-3 years with peanut allergy (clinical symptoms at peanut challenge and IgE >0.1 kU /l to peanut and/or Ara h 2).

Comparison: Three groups are compared. Peanut allergic children are randomized 2:1 to group 1 (active OIT) or group 2 (control). Group 3 consists of age-matched non-allergic children:

Group 1; Children with peanut allergy receiving peanut OIT, slow up-dosing, 40-60 weeks, until the maintenance dose 285 mg peanut protein. Three years' treatment. (n=50 patients)

Group 2; Age-matched children with peanut allergy who do not undergo OIT peanut (peanut avoidance group). Peanut challenges are performed one and three years after inclusion. (n=25 patients)

Group 3; Healthy, non-allergic, age-matched children. No challenges are performed in this group. (n=30 patients)

Group 4; Children not reacting at the baseline peanut challenge (n=9 patients)

Inclusion of study subjects: A review of samples sent to the Karolinska University Laboratory for IgE-ab responses to peanut/Ara h 2 for children in the Stockholm area aged 1-3 years is used for identification of potential participants to whom a letter is sent with information about the study. The families are randomized 2:1 to OIT or control group, group 1 or group 2.

Children without allergies, healthy controls (group 3), will be included from Västerås Hospital.

If children are included in the study but they do not not react at the baseline peanutchallenge, they will not have any intervention (are not eligible to randomisation) and will have a follow-up after 1+3 years (without peanut challenges), group 4.

Outcomes: The primary outcome is defined as sustained unresponsiveness to 750 mg peanut protein (cumulative dose) at an open oral peanut challenge after 3 years of OIT followed by 4-6 weeks of avoidance (group 1 and 2).

Secondary outcomes are adverse events among peanut allergic children with/without OIT treatment (group 1 and 2), and changes in quality of life parameters and immunological markers (group, 1, 2, 3).

Inclusion Criteria:

• Children 1 - 3 years old at inclusion
• Positive baseline challenge at a maximum of the 250 mg peanut protein-dose with at least one objective symptom, or positive peanut challenge performed in the clinic in a similar way within 1 year from study start.
• IgE-ab to peanut and/or Ara h 2 ≥0.1 kUA/l, analyzed within 12 months from start of study
• Written consent for participation in the study from both Guardians

Exclusion Criteria:

• Other serious illness
• Previously life-threatening anaphylaxis (intensive care), regardless of the triggering agent
• A history of eosinophilic esophagitis (EoE), other eosinophilic gastrointestinal disease, severe chronic gastroesophageal reflux disease (GERD), symptoms of dysphagia, unclear recurrent GI disorders
• Participation in another intervention study, if included in intervention Group
• Severe uncontrolled asthma
• Ongoing medication with biological drugs or oral steroids

Blinded randomisation process after a positive baseline peanut challenge (for both participants, care provider and investigator) by opaque envelops.

After the child is randomised to treatment or avoidance, everyone (particpant, care provider and investigator) know if the child is in the treatment or avoidance group.