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Aldehyde Toluidine Blue for Mast Cells

Aldehyde Toluidine Blue

for Mast Cells



Compounding Procedure

  1. Dissolve the dye in the ethanol.
  2. Add paraldehyde and acid.
  3. Ripen one week at room temperature.
  4. Store at room temperature.
  5. Filter before use. Stable for a year or longer.

Tissue Sample

5µ paraffin sections of neutral buffered formalin fixed tissue are suitable. Other fixatives are likely to be satisfactory.


  1. Bring sections to water via xylene and ethanol.
  2. Rinse with 70% ethanol.
  3. Place in solution A for 1 hour.
  4. Wash off excess stain with 70% ethanol.
  5. Rinse well with tap water.
  6. Counterstain with nuclear fast red-tartrazine.
  7. Dehydrate with ethanol, clear with xylene, and mount with a resinous medium.

Expected Results

  • Mast cell granules  –  deep blue
  • Nuclei  –  red
  • Background  –  yellow


  • The staining solution is a modification of Gomori’s aldehyde fuchsin using toluidine blue instead of basic fuchsin.
  • Staining time may need to be increased as the solution ages (up to 2 hours). If staining takes longer than 2 hours, prepare a new solution.
  • Elastic fibres are unstained, likely because basic fuchsin can form dipole-dipole interactions and toluidine blue generally does not.
  • Mucins are stained very pale blue.
  • Different samples of this dye may vary in effectiveness. If a sample gives pale staining, try one from another vendor. Toluidine blue from Fisher Scientific was used to develop the method.

Safety Note

Prior to handling any chemical, consult the Safety Data Sheet (SDS) for proper handling and safety precautions.


  1. Llewellyn, B. D., unpublished.