**4.3.3 Oral food challenge**

Through OFC, the suspected foods should be listed with the classification of type of allergy, and a relevant elimination diet that eliminates only suspected foods should result in an improvement of AD symptoms [2]. The order for the OFC should prioritise NFA before IFA. Additionally, the importance of certain foods should be considered according to the patient's wishes. An OFC for NFA should generally precede an OFC for IFA. Each OFC is conducted according to the relevant protocols.

1. Principle of oral food challenge in AD (Goldmann's triad): intake, elimination diet and challenge test

The diagnosis of food allergy follows the standard principle of Goldmann's triad [19]. When patients show symptoms and signs after the ingestion of suspected causative foods, an elimination diet is initiated. If the patient shows improvement with this diet, the eliminated food is strongly suspected as the cause of AD. If the patient again shows the clinical manifestation with subsequent food challenge, the challenged food is confirmed as the cause of AD.

2. Proper elimination of foods as an absolute condition for OFC

An elimination diet is the first effective way to confirm a food allergy in AD. However, a proper elimination diet is necessary [2]. Unless such a diet is performed, it is likely that elimination will be ineffective. A proper elimination diet is essential and should not be omitted.
