Eosinophilia is characterized by more than 0.5 × 109 eosinophils per liter in the full blood count. A wide range of conditions, from asthma to parasitic infections, autoimmune diseases, and certain forms of cancer, have been known to trigger abnormally high amount of eosinophils. It is essential to reach the correct diagnosis and treat the underlying disease aggresively. Definition of the eosinophilia-myalgia syndrome was offered in 1980s by Centers for Disease Control and Prevention for surveillance purposes, and criteria were revised in 2001, with high specificity. We report a case of 59-year old female who started a special weight-reducing diet regimen that included excessive cashew nut ingestion. Several months after she has presented with periferal blood eosinophilia and constitutional symptoms. Detailed work-up has not found elements for haematological, systemic autoimmune, neoplastic or infectious disease. She was diagnosed with eosinophilia-myalgia syndrome due to extreme L-tryptophan intake, a compound found in the cashew nut’s oil. She responded well to cashew nut withdrawal and steroid therapy. In the follow-up period she remained stable with normal eosinophil count and there was not a need for any specific therapy.