The COFAITH (Clinical Outcomes in Food-AIT trials Harmonization) task force, initiated by the EAACI (European Academy of Allergy and Clinical Immunology), aimed to evaluate and harmonize efficacy outcomes in food allergen immunotherapy (AIT) trials. The task force conducted a systematic review of controlled clinical trials and large case series focusing on milk, egg, and peanut AIT. The review included 63 manuscripts, with 23, 21, and 22 studies for milk, egg, and peanut AIT, respectively. The most common efficacy outcome was desensitization, defined as tolerating a maintenance dose or reaching a specific dose at an oral food challenge (OFC). However, there was significant heterogeneity in the dose definitions. Sustained unresponsiveness and patient-reported outcomes were less frequently explored. OFC methods varied widely, and there was no standardized protocol. The review identified multiple heterogeneous outcomes related to measuring AIT efficacy. The task force made recommendations to standardize and harmonize outcomes and methods to improve the comparability and reliability of future studies. The choice of primary outcome is critical and should be clinically relevant and meaningful to patients and caregivers. The review highlights the need for a consensus on core outcome measures to ensure fully informed decisions about AIT.The COFAITH (Clinical Outcomes in Food-AIT trials Harmonization) task force, initiated by the EAACI (European Academy of Allergy and Clinical Immunology), aimed to evaluate and harmonize efficacy outcomes in food allergen immunotherapy (AIT) trials. The task force conducted a systematic review of controlled clinical trials and large case series focusing on milk, egg, and peanut AIT. The review included 63 manuscripts, with 23, 21, and 22 studies for milk, egg, and peanut AIT, respectively. The most common efficacy outcome was desensitization, defined as tolerating a maintenance dose or reaching a specific dose at an oral food challenge (OFC). However, there was significant heterogeneity in the dose definitions. Sustained unresponsiveness and patient-reported outcomes were less frequently explored. OFC methods varied widely, and there was no standardized protocol. The review identified multiple heterogeneous outcomes related to measuring AIT efficacy. The task force made recommendations to standardize and harmonize outcomes and methods to improve the comparability and reliability of future studies. The choice of primary outcome is critical and should be clinically relevant and meaningful to patients and caregivers. The review highlights the need for a consensus on core outcome measures to ensure fully informed decisions about AIT.