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Stokes’ Congo Red for Amyloid

Stokes' Congo Red

for Amyloid



  • Mayer’s hemalum
  • 80% ethanol
  • Alkaline Congo Red
    Congo redasrequired
    Ethanol, 80%100mL
    Potassium hydroxide0.2g

Compounding Procedure

  1. Dissolve the potassium hydroxide in the ethanol.
  2. Add sufficient dye to saturate. Leave overnight and filter.
  3. Stable for about 3 months.

Tissue Sample

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


  1. Bring sections to water via xylene and ethanol.
  2. Place into alkaline congo red for 25 minutes.
  3. Wash with tap water for 5 minutes.
  4. Stain nuclei with Mayer’s hemalum for 5 minutes.
  5. Blue in running tap water for 10 minutes.
  6. Dehydrate rapidly in absolute ethanol.
  7. Clear with xylene and mount with a resinous medium.

Expected Results

  • Amyloid – orange to red
  • Nuclei – blue
  • Background – colorless


  • If congo red is applied for longer than 25 minutes, the background will show some coloration.
  • Green birefringence is displayed under crossed polarizers.

Safety Note

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


  1. Stokes, Gwen, (1976),
    An improved congo red method for amyloid,
    Medical Laboratory Sciences, v 33, 79