Eosinophilic oesophagitis (EoE) was first described as an orphan disease in the 1990s, but its incidence and prevalence has increased dramatically in the last 20 years. EoE is now the most common cause of dysphagia in young adulthood. EoE is diagnosed endoscopically (with biopsies taken from the oesophagus). Treatment options consist of dietary measures and medications. The latter include PPI (as an off-label medication) and the approved drugs Jorveza (budesonide, topical cortisone preparation) and the monoclonal antibody Dupixent (dupilumab, subcutaneous). The response to therapy is high and the long-term outcome, if treated early, is excellent. However, the disease often remains undetected, mostly due to compensation mechanisms on the part of the patients. Much rarer than EoE are the non-EoE eosinophilic gastrointestinal diseases (EGIDs), in which the eosinophilic tissue infiltration is found in gastrointestinal segments distal to the oesophagus. Their clinical presentation is often non-specific. Pathophysiologically, overlaps with EoE are present. Therapies are also analogous to EoE. An increasing prevalence and incidence is to be expected.