**Background:** Eosinophilic esophagitis (EoE) is a chronic, allergen-triggered, immune-mediated disease characterized by eosinophilic infiltration and esophageal dysfunction. Its incidence reaches up to 20/100,000 inhabitants per year with a prevalence of up to one case/1000 people in Western countries. Clinical symptoms depend on age and disease duration, with dysphagia being the most common complaint and bolus impaction the most common presentation in adults. The natural history of EoE is characterized by a progressive course leading to fibrosis, necessitating life-long therapy. Diet therapy is a first-line anti-inflammatory treatment for EoE, along with proton-pump inhibitors (PPI) and swallowed topical steroids (STS). A distinguishing feature of diet therapy is that it specifically targets the main trigger and cause of the disease, allows identification of triggers, and enables long-term drug-free management.
**Methods:** In January 2023, the authors performed a literature search using PubMed with medical subject heading terms including 'eosinophilic esophagitis', 'diet*', 'therapy', 'treatment', 'intervention' and the qualifier 'adult'. Over 250 studies were identified, and the authors focused on original review articles and case reports/series. This is a narrative review.
**Key Results:** Current guidelines recommend monotherapy with PPI, STS, or diet as the usual initial approach. In cases of inadequate response (>15 eosinophils/high power field), another treatment should be started, with elemental diets reserved as rescue therapy for refractory disease. The British Society of Gastroenterology and BSPGHAN guidelines recommend starting with a two-food elimination diet (2-FED) including milk and gluten-containing cereals before stepping up to four- or six-food elimination diets (4-FED, 6-FED) after endoscopic and histologic evaluation at 8-12 weeks. The multinational prospective 2-4-6 study by Molina-Infante evaluated a step-up strategy in 130 patients (including 25 children). The 2-FED achieved histopathology remission in 43% of patients. Milk was the most frequent trigger (52%), followed by gluten-containing cereals (16%), with both present in 28% of cases. By age stratification, milk was identified as the trigger in 33% of children but only 18% of adults. Remission rates with 4-FED and 6-FED were 60% and 79%, respectively. Most patients (91.6%) had only one or two food triggers. The multistep approach shortened the diagnostic process by 30% and reduced the number of endoscopies by 20%. Food allergy testing-based diets show a response rate of around 50%, with histologic failure calculated at 41% in studies using patch tests and 61% in studies using other tests, though certainty was very low. A meta-analysis reported histological remission with milk elimination alone (1-FED) at approximately 68%, though in adults this drops to 18-25%. Geographical factors influence trigger patterns: in Spain, legumes are a particularly frequent trigger; in the Netherlands, sensitization to birch pollen allergen Bet v 1 and cross-reactive PR-10 foods appears frequent (39%); and in a monocentric Italian study, sensitization to peach LTP (Pru p 3) was present in almost 50% of patients with EoE.
**Clinical Implications:** Dietary therapy is a relevant therapeutic approach due to its allergen-specific anti-inflammatory effect, but it carries risks including malnutrition (especially in milk- and egg-free diets), micronutrient deficiencies (especially in egg-, milk- and wheat-free diets), financial burden, and risk of new allergic sensitizations. Guidelines recommend that dietary therapy be supervised by an expert dietitian with allergy competence, include an allergist in the care team, offer psychological support, and adapt strategies to patient needs. The step-up approach (2-FED to 4-FED to 6-FED) is currently preferred as it is cost-effective and improves compliance. A minimum duration of 6 weeks (usually 8-12) for each elimination step is warranted, followed by endoscopy to confirm remission, then single food reintroduction for 8-12 weeks with rescoping to identify triggers. Unmet needs include defining optimal number and categories of eliminated foods, optimal diet duration, development of new IgE-mediated food allergies, adoption of less invasive endoscopic modalities (such as Cytosponge), and identification of reliable non-invasive biomarkers.