Eosin is a fluorescent red dye resulting from the action of bromine on fluorescein. It can be used to stain cytoplasm, collagen and muscle fibers for examination under the microscope. Structures that stain readily with eosin are termed eosinophilic.



There are actually two very closely related compounds commonly referred to as eosin. Most often used is eosin Y (also known as eosin Y ws, eosin yellowish, Acid Red 87, C.I. 45380, bromoeosine, bromofluoresceic acid, D&C Red No. 22); it has a very slightly yellowish cast. The other eosin compound is eosin B (eosin bluish, Acid Red 91, C.I. 45400, Saffrosine, Eosin Scarlet, or imperial red); it has a very faint bluish cast. The two dyes are interchangeable, and the use of one or the other is a matter of preference and tradition.

Eosin Y is a tetrabromo derivate of fluorescein. [1]

Eosin B is a dibromo dinitro derivate of fluorescein. [2]

Use in histology

Eosin is most often used as a counterstain to haematoxylin in H&E (haematoxylin and eosin) staining. H&E staining is one of the most commonly used techniques in histology. Tissue stained with haematoxylin and eosin shows cytoplasm stained pink-orange and nuclei stained darkly, either blue or purple. Eosin also stains red blood cells intensely red. Eosin is an acidic dye and shows up in the basic parts of the cell, i.e. the cytoplasm. Haematoxylin however is a basic dye and shows up in the acidic part of the cell like the nucleus, where nucleic acids (DNA and RNA) are concentrated.

For staining, eosin Y is typically used in concentrations of 1 to 5 percent weight by volume, dissolved in water or ethanol.[citation needed] For prevention of mold growth in aqueous solutions, thymol is sometimes added (The science of laboratory diagnosis By John Crocker, David Burnett (relevant citation for thymol inhibits growth of fungi). A small concentration (0.5 percent) of acetic acid usually gives a deeper red stain to the tissue.

It is listed as an IARC class 3 carcinogen.


The name Eosin comes from Eos, the Greek word for 'dawn' and the name of the Greek Goddess of the Dawn.[1]

See also


  • Jocelyn H. Bruce-Gregorios, M.D.: Histopathologic Techniques, JMC Press Inc., Quezon City, Philippines, 1974.
  1. ^ Its CAS number is [17372-87-1] and its SMILES structure is O=C5C(Br)=C2O C1=C(Br)C([O-]) =C(Br)C=C1C(C4=C (C([O-])=O)C=C C=C4)=C2C=C3Br.
  2. ^ Its CAS number is [548-28-3] and its SMILES structure is O=C5C(Br)=C2O C1=C(Br)C([O-]) =C([N+]([O-])=O) C=C1C(C4=C(C([O-]) =O)C=CC=C4)=C2 C=C3[N+]([O-])=O.

External links

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Look at other dictionaries:

  • EOSIN — EOSIN, группа кислых двуосновных ок сифталеиновых красок, широко применяемых в микроскоп.технике. Марки: 1. «Eosin», или «Eosin gelblich», или «Eosin wasserlos lich» (Eosin A.. E^osin G., Eosin extra Hochst)… …   Большая медицинская энциклопедия

  • eosin Y — eosin yellowish, eosin Y ws the sodium salt of tetrabromofluorescein, C20H6Br4Na2O5, a water soluble, red, anionic dye of the eosin group; widely used in bacteriologic and histologic staining …   Medical dictionary

  • eosin B — eosin I bluish dibromodinitrofluorescein, a dye having staining properties similar to eosin Y, but having a bluish rather than yellow cast …   Medical dictionary

  • Eosin — E o*sin, n. [Gr. ? dawn.] (Chem.) A yellow or brownish red dyestuff obtained by the action of bromine on fluoresce[ i]n, and named from the fine rose red which it imparts to silk. It is also used for making a fine red ink. Its solution is… …   The Collaborative International Dictionary of English

  • Eosīn — Eosīn, Farbstoff, s. Fluoresceïn …   Meyers Großes Konversations-Lexikon

  • Eosin — Eosin, s. Farbstoffe, künstliche organische …   Lexikon der gesamten Technik

  • Eosin — Eosīn, roter Farbstoff zum Färben von Seide und Wolle, entsteht durch Einwirken von Brom auf Fluoreszeïn, dient zum Papierfärben, zur Herstellung von Lacken und roter Tinte. Eosinophīl (grch.), sich leicht mit E. färbend; eosinophile Zellen, Art… …   Kleines Konversations-Lexikon

  • eosin — [ē′əsin, ē′əsēn΄ē′ō sin, ē′əsin] n. [< Gr ēōs, dawn (see EO ) + IN1] 1. a) a rose colored dye, C20H8O5Br4, prepared by brominating fluorescein and used to color inks, fabrics, etc. and to stain tissues b) its sodium or potassium salt, used as… …   English World dictionary

  • Eosin Y — Strukturformel Allgemeines Name Eosin Y Andere Namen …   Deutsch Wikipedia

  • Eosin B — Strukturformel Allgemeines Name Eosin B Andere Namen …   Deutsch Wikipedia

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