Congo Red Stain

Congo Red Stain
Congo Red Stain


Congo Red Stain

  • Product code: ACMBS-25
  • Specifications: 3x20mL, 3x100mL (Box)
  • Intended use: Intended for qualitative histological staining, selectively staining amyloid in tissues
  • Store temperature: 5℃~30℃
  • Expiry date: 18 Months

More Details

PrincipleMain componentsSample requirementTest procedureResult interpretationPrecautions


Amyloid substance has a selective affinity to Congo red and can be stained readily. Congo red, which is an azo dye with linear configuration, binds hydroxyl of amyloid substance with its amino group while clings on fiber of amyloid substance in parallel and appears red.

Main components

Reagent compositionMain ingredient
1. Congo red solutionCongo red, Methanol
2. Alkaline alcohol solutionPotassium hydroxide
3. Hematoxylin solution (Mayer)Hematoxylin

Sample requirement

  • The tissue section must be fully fixed.

Test procedure

  • 1. The slices are routinely dewaxed to water and washed once with distilled water.
  • 2. Stain in Congo red solution for 10-20 minutes, and pour the dye solution.
  • 3. Differentiate directly in alkaline alcohol solution for several seconds, (under control of the microscope, be faster, otherwise excessive decoloring).
  • 4. Rinse in running water for 5 minutes.
  • 5. Stain nuclei in Mayer Hematoxylin for 2 minutes. Rinse in distilled water for 5 minutes.
  • 6. Conventional dehydration and transparent, sealed with neutral resin.

Result interpretation

Under the polarizing microscope:
Amyloid proteinYellow-green birefringence
Under the light microscope:
Amyloid, red blood cells, and elastic fibersLight pink to red
The backgroundYellowish pink


  • 1. Both amyloid substance and elastin fiber will be stained by the Congo red but appear in different shapes, so distinguish the two carefully.
  • 2. Differentiate appropriately in alkaline alcohol solution. If not enough, collagen fiber will also stain, if excessive, amyloid will discolor, which should be under a microscope control the fitness of differentiation.
  • 3. The unstained amyloid paraffin tissue will gradually lose the affinity to Congo red after one year of storage.
  • 4. This reagent should be used by professionals and interpretation of the results. Read the instruction manual carefully before use, use it within the validity period, and do personal hygiene protection.
  • 5. Dispose of waste according to the requirements of the hospital or environmental protection department after use.
  • 6. The production date, production batch number and expiration date are shown in the outer packaging.


1. Chinese Medical Association. Clinical technical operating specifications-pathology volumes [M]. People's Military Medical Publishing House.

2. Ling Qibo. Practical pathology special staining and histochemistry technology [M]. Guangdong Higher Education Press.

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