This study is a long-term follow-up of participants from the randomized controlled trial (RCT) "Efficacy and Safety of Low-Dose Sesame Oral Immunotherapy in Pediatric Patients", NCT06261554. At the end of the original RCT all participants will undergo an open Oral Food Challenge (OFC) to assess desensitization after 3 months on the maintenance dose of OIT. Patients who have completed the first part of the study will be invited to the current part of the project:

• First arm (initial experimental group) - patients will continue oral immunotherapy (OIT) with low dose of sesame protein (300mg) for the next 8 months (+/- 3 weeks).
• Second arm (initial control group - one year on a sesame elimination diet) - patients will begin OIT following the protocol used in the first part of the study (RCT). Upon completion of this initial phase, they will continue immunotherapy for an additional 8 months (+/- 3 weeks).

After an additional 8 months (+/- 3 weeks) of OIT, all study participants will undergo a 4-week cessation of treatment, followed by an open Oral Food Challenge (OFC) to assess the development of sustained unresponsiveness (SU).

Oral immunotherapy (OIT) is currently considered the most effective treatment for food allergies. The two primary goals of food immunotherapy are desensitization and sustained unresponsiveness.

Desensitization refers to the induction of temporary tolerance to the allergen, which is maintained only through regular, ongoing exposure. In contrast, the most desirable outcome-sustained unresponsiveness-is defined as the continued absence of allergic reactions to the allergen after discontinuation of immunotherapy for a specified period.

This study is a long-term follow-up of participants from the randomized controlled trial (RCT) "Efficacy and Safety of Low-Dose Sesame Oral Immunotherapy in Pediatric Patients", NCT06261554.

Patients who completed the initial phase will be invited to participate in the current phase of the project.

After 8 months (+/- 3 weeks) of continued OIT with a low dose of sesame protein, patients will be admitted for hospital-based assessments including skin prick testing, laboratory evaluations, and an open oral food challenge (OFC) to assess the acquisition of desensitization to sesame protein.

Patients who had a negative OFC (indicating confirmed desensitization) after 3 months of OIT during the initial phase of the study will proceed to the next part without undergoing another OFC prior to the treatment break. Only patients with confirmed desensitization, as evidenced by a negative OFC, will be eligible for the next phase.

Following a 4-week interruption in OIT, these patients will be invited for another Oral Food Challenge (OFC) to assess the acquisition of sustained unresponsiveness to sesame protein.

Patients with a positive OFC prior to the treatment break (i.e., those who did not achieve desensitization)-regardless of their original study group-will continue sesame OIT in accordance with the standard desensitization protocol used at the Clinic.

An interim analysis is planned after 50% of participants have completed the primary outcome assessment. The analysis will be conducted by an independent Data Monitoring Committee to evaluate safety and efficacy. Appropriate alpha-spending adjustments will be applied to control for Type I error.

Inclusion criteria:

• Sesame allergy confirmed before starting immunotherapy
• Completion of the first part of the study - achieving the maintenance dose (300mg sesame protein) during immunotherapy
• Obtaining informed consent to participate in the study,
• Patient/carer cooperation.

Exclusion criteria:

• Severe asthma,

• Mild/moderate poorly controlled asthma: FEV1<80% (under 5. percentile), FEV1/FVC<75% (under 5. percentile), hospitalisation for asthma exacerbation in the last 12 months,

• Oral/sublingual/subcutaneous immunotherapy against other allergens in the first year/season of immunotherapy

• Eosinophilic gastroenteritis,

• Severe, recurrent episodes of anaphylaxis within the last 6 months,

• Chronic diseases requiring ongoing treatment, including heart disease, epilepsy, metabolic diseases, diabetes,

• Taking medication:

  • oral, daily steroid therapy >1 month in the past 12 months,
  • At least two courses of oral steroid therapy (at least 7 days) within the last 12 months,
  • One oral steroid therapy (min. 7 days) in the last 3 months,
  • biological treatment,
  • therapy with β-blockers, ACE-inhibitors, calcium channel inhibitors,

• Pregnancy,

• No consent to participate in the study,

• Lack of cooperation from the patient.

Well-controlled asthma, allergic rhinitis, atopic dermatitis are not considered exclusion criteria.

Deidentified individual participant data underlying the results of this study-including text, tables, figures, and appendices-will be made available upon reasonable request to the author of this protocol, subject to ethical approval and data sharing agreements.