Congo Red

Dye content ≥35 %

Cosmos Red, Direct Red 28, Cotton Red C, Congo Red 4B, Cotton Red B, Direct Red R, Direct Red Y
Empirical Formula (Hill Notation):
CAS Number:
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Quality Level




Dye content, ≥35%


hematology: suitable
histology: suitable
titration: suitable


6.7 (10 g/L)


>360 °C (lit.)


H2O: 1 mg/mL

Featured Industry

Diagnostic Assay Manufacturing

storage temp.

room temp

SMILES string




InChI key


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  • Congo red has been used as a histochemical stain for the quantification of amyloid deposits in brain tissues.
  • It has been used as a cell wall inhibiting agent in fungus Cryptococcus neoformans.
  • It has also been used to study microstructural details in the cell walls of raw potato and fried potato using confocal microscopy.


25, 100 g in poly bottle

Biochem/physiol Actions

Congo red is a benzidine-based anionic diazo dye. It is a histological dye which binds to many amyloid proteins and is used for the quantification of amyloid β-peptide aggregation. Congo red also interacts with β-D-glucans, polysaccharides containing continuous β-(1→4)-linked D-glucopyranosyl units and some hemicellulosic galactoglucomannans.


Health hazard

Signal Word


Hazard Statements


Carc. 1B - Repr. 2


6.1C - Combustible, acute toxic Cat.3 / toxic compounds or compounds which causing chronic effects

WGK Germany


Personal Protective Equipment

dust mask type N95 (US),Eyeshields,Gloves

Certificate of Analysis

Certificate of Origin

  1. Which document(s) contains shelf-life or expiration date information for a given product?

    If available for a given product, the recommended re-test date or the expiration date can be found on the Certificate of Analysis.

  2. How do I get lot-specific information or a Certificate of Analysis?

    The lot specific COA document can be found by entering the lot number above under the "Documents" section.

  3. How do I find price and availability?

    There are several ways to find pricing and availability for our products. Once you log onto our website, you will find the price and availability displayed on the product detail page. You can contact any of our Customer Sales and Service offices to receive a quote.  USA customers:  1-800-325-3010 or view local office numbers.

  4. What is the Department of Transportation shipping information for this product?

    Transportation information can be found in Section 14 of the product's (M)SDS.To access the shipping information for this material, use the link on the product detail page for the product. 

  5. Why does the SDS for Congo Red list carcinogen as an OSHA hazard, (Section 2) but in Section 11 on carcinogenicity, it states that there is no component identified as a carcinogen?

     The reason that there is not an OSHA listing for carcinogens on most of SDS that have a hazard of a carcinogen hazard  is because that section of the SDS is specifically for the OSHA regulated carcinogens, also referred to as the OSHA 13.Congo red at this time is not specifically called out as a carcinogen by the other 3 Organizations listed (IARC, NTP, ACGIH) either. Congo red is listed by the European Classification Labeling & Packaging (CLP) Regulation (which is a pretty definitive guide for hazard classification), as a carcinogen. No other organizations have had the time to classify this material at this time. This is why it is only listed as a carcinogen in section 2 and in section 15.

  6. My question is not addressed here, how can I contact Technical Service for assistance?

    Ask a Scientist here.

  7. My question is not addressed here, how can I contact Technical Service for assistance?

    Ask a Scientist here.

Some changes in potato chips during frying observed by confocal laser scanning microscopy (CLSM).
Pedreschi F and Aguilera JM
Food Science and Technology International = Ciencia y tecnologia de Los Alimentos Internacional, 8, 197-201 (2002)
Kinetic study and equilibrium isotherm analysis of Congo Red adsorption by clay materials.
Chemical Engineering Journal, 148, 354-364 (2009)
Anat Frydman-Marom et al.
PloS one, 6(1), e16564-e16564 (2011-02-10)
An increasing body of evidence indicates that accumulation of soluble oligomeric assemblies of β-amyloid polypeptide (Aβ) play a key role in Alzheimer's disease (AD) pathology. Specifically, 56 kDa oligomeric species were shown to be correlated with impaired cognitive function in...
PKC1 is essential for protection against both oxidative and nitrosative stresses, cell integrity, and normal manifestation of virulence factors in the pathogenic fungus Cryptococcus neoformans.
Gerik KJ, et al.
Eukaryotic Cell, 7, 1685-1685 (2008)
Quantification of cerebral amyloid angiopathy and parenchymal amyloid plaques with Congo red histochemical stain.
Wilcock DM, et al.
Nature Protocols, 1, 1591-1591 (2006)

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