Mast cells are found in bone marrow, blood, mucosal, and connective tissues. They migrate into the loose connective tissue of all organs. They play a major role in many physiologic processes however as discussed in this article they can become an aggressive force which can damage the natural biological balance

We report a 56-year-old male with methemoglobinemia and hemolytic anemia, secondary to fava bean ingestion. Methylene blue administration worsened the hemolysis as he was G6PD deficient but not diagnosed before. We have discussed the mechanism of hemolysis in such patients and the management of such cases.