Toxic granulation appears as dark blue-black granules in the cytoplasm of neutrophils.
These granules are thought to be primary granules. Artifactual heavy granulation caused by poor staining is seen evenly spread throughout each cell and in all granulocytes, whereas toxic granulation is unevenly spread throughout the cytoplasm of certain cells. Large amounts of toxic granulation can give the neutrophil a bluish appearance. Toxic granulation is a stress response to acute infections, burns, and drug poisoning.