The goal of this study is to set up a paediatric observatory within the allergology department of The saint Vincent Hospital, Lille. The study aims to:

• Collect exhaustive prospective data from patients eligible for oral immunotherapy.

This prospective observatory will enable statistical analyses to be carried out on common food allergens such as hazelnut, cashew nut, pistachio and others.

During the consultation, the allergist will inform the legal representative and the child about the terms of the study, and will provide them with an information note specifying the objectives of the study and its terms, the involvement of the child and his or her rights.

Depending on the allergen involved, the oral immunotherapy session will be assigned to one of three study groups: 1) allergen to hazelnut, walnut, pistachio, cashew or peanut,2) allergen to cow's milk, wheat or egg, 3) allergen to unusual foods: sesame, celery, fenugreek, peas, lentils, etc.

For each patient, and for each visit during the treatment period the collection of anthropometric, sociodemographic and medical data relating to oral food challenge will be done

Oral immunotherapy will then be started in accordance with standard practice. During this first visit, the investigator will give the patient a diary in which to record information about any IgE-mediated side-effects of the oral immunotherapy. Subsequent visits will follow the patient's usual routine until the desensitisation threshold is reached or the patient decides to stop the oral immunotherapy protocol. Visits will be made every 6 months, with a window of two months around each date.During these monitoring visits, tthe collection of anthropometric, sociodemographic and medical data relating to oral food challenge will be continue.

During each visit, a new food challenge test may be performed at the investigator's discretion to assess a new reactogenic threshold. Following this test, the following data will be collected:

• the cumulative dose ingested (mg food and mg food protein)
• the grade of the reaction (from 0 to 5 according to the Astier et Coll classification)
• achievement of desensitisation

A patient begins oral immunotherapy following food challenge test in a day hospital. Thus, a patient consulting at different times for several allergies and eligible for several oral immunotherapies will be able to take part in the study for several allergens. The follow-up of the different oral immunotherapies started (maximum 2 simultaneously, but could go up to 5, 6... over time) will be distinct. The patient may therefore participate several times in the study: in different groups, or in the same group, for different allergens. All the above data are collected separately for each new oral immunotherapy (except for socio-demographic data and information on previous oral immunotherapies, which are collected only at the time of inclusion).

In very rare cases, a patient may undergo several oral immunotherapies for the same allergen, but only the first oral immunotherapy (from the time the observatory was set up) will be taken into account in this study. If oral immunotherapy for the same allergen has already been carried out before the observatory was set up, the second oral immunotherapy for this allergen will not be included in the study, as its results will be biased.

Inclusion criteria:

• patient under 15 years and 9 months,
• positive diagnosis of food allergy (positive food challenge test or "highly probable allergy", defined by a convincing history, a positive prick test and IgE > 0.35 kUA/L),
• eligible for oral food challenge
• accepting the following allergens : hazelnut, walnut, pistachio, cashew, peanut, cow's milk, wheat, egg, sesame, celery, fenugreek, pea, lentils or others

Exclusion criteria:

• Opposition
• Already received oral challenge for the same allergen.

All eligible patients consulting at the allergology service of the Saint Vincent Hospital, Lille, France will be informed and included, unless they object.