At present there is no cure for food allergy. People with a food allergy need to avoid the food they are allergic to in order to stay safe. However we know that accidental exposure is common. Researchers have begun to look at the effectiveness of 'oral immunotherapy' as a treatment for food allergy but results have been mixed.

This study is a randomized controlled trial to evaluate the effectiveness of Probiotic and Peanut Oral Immunotherapy (PPOIT) in inducing tolerance in children with peanut allergy compared with Oral Immunotherapy (OIT) alone and with Placebo. Children will take increasing doses of peanut protein and a set amount of probiotic until a total of 18 months treatment is completed. Children will be tested for peanut allergy at the start of the study, at the end of PPOIT treatment T1 (18 months) and T2 (8 weeks) and T3 (1year) after treatment.

This is a three-armed, randomised (4:4:1), stratified (by age), blinded, placebo-controlled, parallel-group, superiority trial.

1. PPOIT Probiotic and peanut OIT taken daily for 18 months.
2. OIT Probiotic placebo and peanut OIT taken daily for 18 months.
3. Placebo Probiotic placebo and OIT placebo taken daily for 18 months.

The study consists of:

Screening visit occurs within three months before Day 1.

Day 1 Rush Induction Phase is the start of treatment where participants receive increasing doses of peanut (or placebo) OIT every 20 minutes to reach a final dose of 12mg of peanut protein (or placebo). A single dose of 2x10^10 cfu Lactobacillus rhamnosus GG (or placebo) is also taken.

Week 1 - 16 is the Buildup Phase where the daily dose of peanut (or placebo) OIT is increased every 2 weeks* until a maintenance dose of 2000mg peanut protein (or placebo) is reached. This is expected to take 16 weeks. A fixed daily dose of 2x10^10 cfu Lactobacillus rhamnosus GG (or placebo) is taken during this phase.

* In unavoidable circumstances i.e. school camps, examinations, when scheduling must be amended depending on parents/ participants availability, the window for buildup visits can be +/- 7 days.

Week 16 - 78 is the Maintenance Phase where participants take a daily dose of 2g of peanut protein (or placebo) and a daily dose of 2x10^10 cfu Lactobacillus rhamnosus GG (or placebo) at home and continue until a total of 18 months of treatment is completed.

Week 78 - 86 is the Elimination Phase where participants continue on a peanut-elimination diet post-treatment.

Week 86 -130 is the Monitoring Phase: All groups will be followed up for 12 months after the treatment period. During this time, at 6 months, a telephone interview will be conducted with the participant's parent or guardian to collect information on exposure to peanut/amount of peanut being eaten and allergic reactions.

The primary outcome analysis will be conducted when all subjects have either completed the T2 DBPCFC or terminated the study prior to their T2 visit. Analysis of safety and tolerability, and other secondary outcomes to the T2 timepoint will also be conducted at this time. A supplemental analysis will be conducted at the end of study (i.e. when last subject completes T3 or has withdrawn from the study prior to their T3 visit, or sponsor terminates the study), using cumulative data from the study.

Inclusion Criteria: Subjects are eligible if they meet all of the following criteria

• Aged between 1 year and 17 years of age;
• >=7kg (the weight considered safe for administration of adrenaline autoinjector (e.g. Jext);
• Ethnic Chinese; and
• Confirmed diagnosis of peanut allergy as defined by a failed double-blind placebo-controlled food challenge (DBPCFC) with peanut and a serum peanut-specific IgE level of at least 0.35 kUA (allergen-specific unit) per liter according to ImmunoCAP (Thermo Fisher Scientific) at screening.

Exclusion Criteria: Subjects are not eligible if they meet any of the following criteria

• History of severe anaphylaxis (as defined by persistent hypotension, collapse, loss of consciousness, persistent hypoxia or ever needing >3 doses of intramuscular adrenaline or an intravenous adrenaline infusion for management of an allergic reaction);
• Severe anaphylaxis during the study entry DBPCFC (defined as persistent hypotension, collapse, loss of consciousness, persistent hypoxia, or requiring >3 doses of intramuscular adrenaline or an intravenous adrenaline infusion for management of an allergic reaction);
• FEV1 <85% at rest and FEV1/FVC ≤ 85% at rest or ongoing chronic persistent asthma (as per Australian Asthma Foundation guidelines);
• Underlying medical conditions (e.g. cardiac disease) that increase the risks for anaphylaxis;
• Use of beta-blockers, and ACE inhibitors;
• Inflammatory intestinal conditions, indwelling catheters, gastrostomies, immunocompromised states, post-cardiac and/or gastrointestinal tract surgery, critically-ill or other conditions that may increase the risks of probiotic associated sepsis;
• Already taking probiotic supplements or foods containing probiotics within the past month;
• Reacting to the placebo component during the study entry DBPCFC;
• Have received other food immunotherapy treatment in the preceding 12 months;
• History of suspected or biopsy-confirmed eosinophilic esophagitis (EoE);
• Currently taking immunomodulatory therapy (including allergen immunotherapy);
• Past or current major illness that in the opinion of the Site Investigator may affect the subject's ability to participate in the study e.g. increased risk to the participant;
• Subjects who in the opinion of the Site Investigator are unable to follow the protocol;
• Another family member already enrolled in the trial (to maintain safety and blinding); or
• Non-English and non-Chinese speaking participants and their families. NOTE: participants with other food allergies are NOT excluded from participating in this trial.