Giemsa stain is based on the use of the Giemsa dye, a neutral blue dye consisting of an acid dye, eosin, and a basic dye, methylene azide, which is metachromatic (= which has the the property of giving certain fabrics a hue different from their own color). An acetic acid bath makes it possible to eliminate the excess of blue and to reveal the various tissue elements whose coloration varies according to the molecules fixed by the dye.

Giemsa stain makes it possible to demonstrate the presence of microorganisms in all types of tissues. It can especially be used to detect the presence of Helicobacter pylori in the diagnosis of gastric ulcers or chronic gastritis. It can also detect the parasite Leishmaniasis or the fungus Aspergillus niger which may be responsible for pulmonary mycosis. It also makes it possible to visualize the different blood cells in the hematopoietic tissues.

Giemsa stain is performed on paraffin sections. It is used to stain the blood cells of hematopoietic tissues. It can also be applied to all tissue sections in which the presence of microorganisms is suspected. Gram + and Gram Bacteria are not differentiated with this staining.

Here are some examples of stains obtained with the Giemsa stain:

• Helicobacter pylori: blue, with its characteristic shape in "seagull flight"
• Cores: Blue
• Cytoplasm: Rose