Acridine orange is theoretically intended to stain viable cells, and if low intensity is observed, particularly when using a light microscope, it is likely true. However, for visualizing viable cells stained with acridine orange, a fluorescent microscope is routinely used. For simple neutrophil counting in saliva, acridine orange may not be the best choice due to cost considerations.
While Giemsa solutions can be used, staining can be challenging, and often there are no published procedures for using Wright, Wright Giemsa, or Giemsa solution for counting neutrophils under a hemacytometer. The recommended product for this purpose is Crystal Violet or Turks/Tuerks solution, a simple solution of crystal violet dissolved in water. Acetic acid is sometimes added to the Turks solution to lyse red blood cells, but if the saliva is not bloody, adding acetic acid is unnecessary.
