All Photos(2)



Congo Red

certified by the Biological Stain Commission, BioXtra

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:
Molecular Weight:
Colour Index Number:
EC Number:
MDL number:
PubChem Substance ID:

Quality Level


certified by the Biological Stain Commission

product line





Dye content, ≥85%


>360 °C (lit.)


H2O: 10 mg/mL


diagnostic assay manufacturing

storage temp.

room temp

SMILES string




InChI key


Looking for similar products? Visit Product Comparison Guide


Congo red has been used for the staining of β amyloid peptides.


25 g in glass 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.


Certified for use as a counterstain for alum based hematoxylin and in the Highman or the Churukian modification of Puchtler′s amyloid stain.


Health hazard

Signal Word


Hazard Statements

Hazard Classifications

Carc. 1B - Repr. 2

Storage Class Code

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



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.

Long-term treatment of thalidomide ameliorates amyloid-like pathology through inhibition of ?-secretase in a mouse model of Alzheimer's disease.
He P, et al.
PLoS ONE, 8, e55091-e55091 (2013)
Alejandro Llanos-Chea et al.
Journal of pediatric gastroenterology and nutrition, 68(4), 509-516 (2018-11-13)
Enteric bacterial pathogens cause diarrheal disease and mortality at significant rates throughout the world, particularly in children younger than 5 years. Our ability to combat bacterial pathogens has been hindered by antibiotic resistance, a lack of effective vaccines, and accurate
Efficient imaging of amyloid deposits in Drosophila models of human amyloidoses.
Berg I, et al.
Nature Protocols, 5, 935-935 (2010)
Quantifying amyloid beta-peptide (Abeta) aggregation using the Congo red-Abeta (CR-abeta) spectrophotometric assay.
Klunk WE, et al.
Analytical Biochemistry, 266, 66-66 (1999)
Eric K Chu et al.
Nature communications, 9(1), 4087-4087 (2018-10-07)
Bacterial biofilms represent an important medical problem; however, the mechanisms of the onset of biofilm formation are poorly understood. Here, using new controlled methods allowing high-throughput and reproducible biofilm growth, we show that biofilm formation is linked to self-imposed mechanical

Our team of scientists has experience in all areas of research including Life Science, Material Science, Chemical Synthesis, Chromatography, Analytical and many others.

Contact Technical Service