Eosinophilia is a condition in which the number of eosinophils in the peripheral blood or tissues increases above the normal level. Threshold values for eosinophilia change with age, remaining the highest in infants and young children. Hypereosinophilia is rare and requires detailed diagnosis. The causes of eosinophilia vary. The literature distinguishes its primary form – associated with bone marrow proliferative diseases, and the condition secondary to many diseases, most commonly parasitic infections and allergic reactions. The secondary form of eosinophilia is most frequent in children. Chronic activation of eosinophils can lead to fibrosis and thrombotic changes in tissues affected by infiltration. In the paediatric population, contrary to adults, these pathological processes are more common in the gastrointestinal tract. Hypereosinophilia is rare in infants, which favours diagnostic and therapeutic concerns. In this paper, we present a case of a 10-month-old infant with hypereosinophilia coexisting with lambliosis and food intolerance.