Fluorescein
Overview
 
Fluorescein is a synthetic organic compound
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

 available as a dark orange/red powder soluble in water and alcohol. It is widely used as a fluorescent tracer
Flow tracer
thumb|right|300px|On May 2, [[2001]], the Moderate-resolution Imaging Spectroradiometer obtained this spectacular image of the [[Atlantic Ocean]]'s [[Gulf Stream]]. The [[false color]]s in the image represent "[[brightness temperature]]" observed at the top of the [[atmosphere]]...

 for many applications.

Fluorescein is a fluorophore
Fluorophore
A fluorophore, in analogy to a chromophore, is a component of a molecule which causes a molecule to be fluorescent. It is a functional group in a molecule which will absorb energy of a specific wavelength and re-emit energy at a different wavelength...

 commonly used in microscopy
Microscopy
Microscopy is the technical field of using microscopes to view samples and objects that cannot be seen with the unaided eye...

, in a type of dye laser
Dye laser
A dye laser is a laser which uses an organic dye as the lasing medium, usually as a liquid solution. Compared to gases and most solid state lasing media, a dye can usually be used for a much wider range of wavelengths. The wide bandwidth makes them particularly suitable for tunable lasers and...

 as the gain medium, in forensics
Forensics
Forensic science is the application of a broad spectrum of sciences to answer questions of interest to a legal system. This may be in relation to a crime or a civil action...

 and serology
Serology
Serology is the scientific study of blood serum and other bodily fluids. In practice, the term usually refers to the diagnostic identification of antibodies in the serum...

 to detect latent blood stains, and in dye tracing
Dye tracing
Dye tracing is tracking and tracing various flows using dye added to the liquid in question. The purpose of tracking may be an analysis of the flow itself, of the transport of something by the flow of the objects that convey the flow...

. Fluorescein has an absorption maximum at 494 nm and emission
Fluorescence
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation of a different wavelength. It is a form of luminescence. In most cases, emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation...

 maximum of 521 nm (in water).
Encyclopedia
Fluorescein is a synthetic organic compound
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

 available as a dark orange/red powder soluble in water and alcohol. It is widely used as a fluorescent tracer
Flow tracer
thumb|right|300px|On May 2, [[2001]], the Moderate-resolution Imaging Spectroradiometer obtained this spectacular image of the [[Atlantic Ocean]]'s [[Gulf Stream]]. The [[false color]]s in the image represent "[[brightness temperature]]" observed at the top of the [[atmosphere]]...

 for many applications.

Fluorescein is a fluorophore
Fluorophore
A fluorophore, in analogy to a chromophore, is a component of a molecule which causes a molecule to be fluorescent. It is a functional group in a molecule which will absorb energy of a specific wavelength and re-emit energy at a different wavelength...

 commonly used in microscopy
Microscopy
Microscopy is the technical field of using microscopes to view samples and objects that cannot be seen with the unaided eye...

, in a type of dye laser
Dye laser
A dye laser is a laser which uses an organic dye as the lasing medium, usually as a liquid solution. Compared to gases and most solid state lasing media, a dye can usually be used for a much wider range of wavelengths. The wide bandwidth makes them particularly suitable for tunable lasers and...

 as the gain medium, in forensics
Forensics
Forensic science is the application of a broad spectrum of sciences to answer questions of interest to a legal system. This may be in relation to a crime or a civil action...

 and serology
Serology
Serology is the scientific study of blood serum and other bodily fluids. In practice, the term usually refers to the diagnostic identification of antibodies in the serum...

 to detect latent blood stains, and in dye tracing
Dye tracing
Dye tracing is tracking and tracing various flows using dye added to the liquid in question. The purpose of tracking may be an analysis of the flow itself, of the transport of something by the flow of the objects that convey the flow...

. Fluorescein has an absorption maximum at 494 nm and emission
Fluorescence
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation of a different wavelength. It is a form of luminescence. In most cases, emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation...

 maximum of 521 nm (in water). The major derivatives are fluorescein isothiocyanate
Isothiocyanate
Isothiocyanate is the chemical group –N=C=S, formed by substituting sulfur for oxygen in the isocyanate group. Many natural isothiocyanates from plants are produced by enzymatic conversion of metabolites called glucosinolates. These natural isothiocyanates, such as allyl isothiocyanate, are also...

 (FITC
Fluorescein isothiocyanate
Fluorescein isothiocyanate is a derivative of fluorescein used in wide-ranging applications including flow cytometry. FITC is the original fluorescein molecule functionalized with an isothiocyanate reactive group , replacing a hydrogen atom on the bottom ring of the structure...

) and, in oligonucleotide synthesis
Oligonucleotide synthesis
Oligonucleotide synthesis is the chemical synthesis of relatively short fragments of nucleic acids with defined chemical structure . The technique is extremely useful in current laboratory practice because it provides a rapid and inexpensive access to custom-made oligonucleotides of the desired...

, 6-FAM phosphoramidite
Fluorescein amidite
Fluorescein amidite, abbreviated as FAM , is an important synthetic equivalent of fluorescein dye used in oligonucleotide synthesis and molecular biology...

.

Fluorescein also has an isosbestic point
Isosbestic point
In spectroscopy, an isosbestic point is a specific wavelength at which two chemical species have the same molar absorptivity or -more generally- are linearly related...

 (equal absorption for all pH values
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

) at 460 nm. Fluorescein is also known as a color additive (D&C
Federal Food, Drug, and Cosmetic Act
The United States Federal Food, Drug, and Cosmetic Act , is a set of laws passed by Congress in 1938 giving authority to the U.S. Food and Drug Administration to oversee the safety of food, drugs, and cosmetics. A principal author of this law was Royal S. Copeland, a three-term U.S. Senator from...

 Yellow no. 7). The disodium salt form of fluorescein is known as uranine or D&C
Federal Food, Drug, and Cosmetic Act
The United States Federal Food, Drug, and Cosmetic Act , is a set of laws passed by Congress in 1938 giving authority to the U.S. Food and Drug Administration to oversee the safety of food, drugs, and cosmetics. A principal author of this law was Royal S. Copeland, a three-term U.S. Senator from...

 Yellow no. 8.

The color of its aqueous solution varies from green to orange as a function of the way it is observed: by reflection or by transmission, as it can be noticed in bubble levels
Spirit level
A spirit level or bubble level is an instrument designed to indicate whether a surface ishorizontal or vertical . Different types of spirit levels may be used by carpenters, stonemasons, bricklayers, other building trades workers, surveyors, millwrights and other metalworkers, and in some...

 in which fluorescein is added as a colorant to the alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....

 filling the tube to increase the visibility of the air bubble and the precision of the instrument.

Chemical and physical properties

The fluorescence of this molecule is very high, and excitation occurs at 494 nm
Nanometre
A nanometre is a unit of length in the metric system, equal to one billionth of a metre. The name combines the SI prefix nano- with the parent unit name metre .The nanometre is often used to express dimensions on the atomic scale: the diameter...

 and emission at 521 nm.

Fluorescein has a pKa
Acid dissociation constant
An acid dissociation constant, Ka, is a quantitative measure of the strength of an acid in solution. It is the equilibrium constant for a chemical reaction known as dissociation in the context of acid-base reactions...

 of 6.4, and its ionization equilibrium leads to pH-dependent absorption and emission
Fluorescence
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation of a different wavelength. It is a form of luminescence. In most cases, emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation...

 over the range of 5 to 9. Also, the fluorescence lifetimes of the protonated and deprotonated forms of fluorescein are approximately 3 and 4 ns, which allows for pH determination from nonintensity based measurements. The lifetimes can be recovered using time-correlated single photon counting or phase-modulation fluorimetry.

Derivatives

There are many fluorescein derivatives. For example, fluorescein isothiocyanate
Fluorescein isothiocyanate
Fluorescein isothiocyanate is a derivative of fluorescein used in wide-ranging applications including flow cytometry. FITC is the original fluorescein molecule functionalized with an isothiocyanate reactive group , replacing a hydrogen atom on the bottom ring of the structure...

 1, often abbreviated as FITC, is the original fluorescein molecule functionalized with an isothiocyanate
Isothiocyanate
Isothiocyanate is the chemical group –N=C=S, formed by substituting sulfur for oxygen in the isocyanate group. Many natural isothiocyanates from plants are produced by enzymatic conversion of metabolites called glucosinolates. These natural isothiocyanates, such as allyl isothiocyanate, are also...

 group (-N=C=S), replacing a hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

 atom on the bottom ring of the structure. This derivative is reactive towards primary amine
Amine
Amines are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group. Important amines include amino acids, biogenic amines,...

 groups of biologically relevant compounds including intracellular proteins to form a thiourea linkage. A succinimidyl ester functional group attached to the fluorescein core, creating NHS-fluorescein, forms another common amine-reactive derivative, yielding more stable amide adducts. Pentafluorophenyl esters
Pentafluorophenyl esters
Pentafluorophenyl esters chemistry typically used to attach fluorophores or haptens to the primary amines of biomolecules. They produce as strong amide bound than succinimidyl esters , but PFP esters are less susceptible to spontaneous hydrolysis during conjugation reactions....

 (PFP) and tetrafluorophenyl esters
Tetrafluorophenyl esters
Tetrafluorophenyl esters chemistry typically used to attach fluorophores or haptens to the primary amines of biomolecules. They produce as strong amide bound than succinimidyl esters , but TFP esters are less susceptible to spontaneous hydrolysis during conjugation reactions...

 (TFP) are other useful reagents. In oligonucleotide synthesis
Oligonucleotide synthesis
Oligonucleotide synthesis is the chemical synthesis of relatively short fragments of nucleic acids with defined chemical structure . The technique is extremely useful in current laboratory practice because it provides a rapid and inexpensive access to custom-made oligonucleotides of the desired...

, several phosphoramidite reagents containing protected fluorescein, e.g. 6-FAM phosphoramidite
Fluorescein amidite
Fluorescein amidite, abbreviated as FAM , is an important synthetic equivalent of fluorescein dye used in oligonucleotide synthesis and molecular biology...

 2, are widely used for the preparation of fluorescein-labeled oligonucleotide
Oligonucleotide
An oligonucleotide is a short nucleic acid polymer, typically with fifty or fewer bases. Although they can be formed by bond cleavage of longer segments, they are now more commonly synthesized, in a sequence-specific manner, from individual nucleoside phosphoramidites...

s.

Other green dyes include Oregon Green, Tokyo Green, SNAFL, and carboxynaphthofluorescein. These dyes, along with newer fluorophore
Fluorophore
A fluorophore, in analogy to a chromophore, is a component of a molecule which causes a molecule to be fluorescent. It is a functional group in a molecule which will absorb energy of a specific wavelength and re-emit energy at a different wavelength...

s such as Alexa 488
Alexa (fluor)
The Alexa Fluor family of fluorescent dyes is produced by Molecular Probes, a subsidiary of Invitrogen. Alexa Fluor dyes are typically used as cell and tissue labels in fluorescence microscopy and cell biology....

, FluoProbes 488
Fluoprobes
The FluoProbes series of fluorescent dyes were developed by Interchim to improve performances of standard fluorophores. They are designed for labeling biomolecules, cells, tissues or beads in advanced fluorescent detection techniques....

 and DyLight 488
DyLight Fluor
The DyLight Fluor family of fluorescent dyes are produced by Dyomics in collaboration with Thermo Fisher Scientific. DyLight dyes are typically used in biotechnology and research applications as biomolecule, cell and tissue labels for fluorescence microscopy, cell biology or molecular...

, have been tailored for various chemical and biological applications where higher photostability
Photobleaching
Photobleaching is the photochemical destruction of a fluorophore. In microscopy, photobleaching may complicate the observation of fluorescent molecules, since they will eventually be destroyed by the light exposure necessary to stimulate them into fluorescing...

, different spectral characteristics, or different attachment groups are needed.

Synthesis

Fluorescein was first synthesized by Adolf von Baeyer
Adolf von Baeyer
Johann Friedrich Wilhelm Adolf von Baeyer was a German chemist who synthesized indigo, and was the 1905 recipient of the Nobel Prize in Chemistry. Born in Berlin, he initially studied mathematics and physics at Berlin University before moving to Heidelberg to study chemistry with Robert Bunsen...

 in 1871. It can be prepared from phthalic anhydride
Phthalic anhydride
Phthalic anhydride is the organic compound with the formula C6H42O. It is the anhydride of phthalic acid. This colourless solid is an important industrial chemical, especially for the large-scale production of plasticizers for plastics. In 2002, approximately 4.6 billion kilograms were...

 and resorcinol
Resorcinol
Resorcinol is a dihydroxy benzene. It is the 1,3-isomer of benzenediol with the formula C6H42.-Nomenclature:Benzene-1,3-diol is the name recommended by the International Union of Pure and Applied Chemistry in its 1993 Recommendations for the Nomenclature of Organic Chemistry.-Production:It is...

 in the presence of zinc chloride
Zinc chloride
Zinc chloride is the name of chemical compound with the formula ZnCl2 and its hydrates. Zinc chlorides, of which nine crystalline forms are known, are colorless or white, and are highly soluble in water. ZnCl2 itself is hygroscopic and even deliquescent. Samples should therefore be protected from...

 via the Friedel-Crafts reaction
Friedel-Crafts reaction
The Friedel–Crafts reactions are a set of reactions developed by Charles Friedel and James Crafts in 1877. There are two main types of Friedel–Crafts reactions: alkylation reactions and acylation reactions. This reaction type is a form of electrophilic aromatic substitution...

.
A second method to prepare fluorescein uses methanesulfonic acid
Methanesulfonic acid
Methanesulfonic acid is a colorless liquid with the chemical formula CH3SO3H. It is the simplest of the alkylsulfonic acids. Salts and esters of methanesulfonic acid are known as mesylates. Methanesulfonic acid is used as an acid catalyst in organic reactions because it is non-volatile, strong acid...

 as a Brønsted acid catalyst. This route has a high yield under milder conditions.

Biochemical research

In cellular biology, the isothiocyanate
Isothiocyanate
Isothiocyanate is the chemical group –N=C=S, formed by substituting sulfur for oxygen in the isocyanate group. Many natural isothiocyanates from plants are produced by enzymatic conversion of metabolites called glucosinolates. These natural isothiocyanates, such as allyl isothiocyanate, are also...

 derivative of fluorescein is often used to label and track cells
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....

 in fluorescence microscopy applications (for example, flow cytometry
Flow cytometry
Flow cytometry is a technique for counting and examining microscopic particles, such as cells and chromosomes, by suspending them in a stream of fluid and passing them by an electronic detection apparatus. It allows simultaneous multiparametric analysis of the physical and/or chemical...

). Additional biologically active molecules (such as antibodies
Antibody
An antibody, also known as an immunoglobulin, is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, termed an antigen...

) may also be attached to fluorescein, allowing biologists to target the fluorophore to specific proteins or structures within cells. This application is common in yeast display
Yeast display
Yeast display is a technique used in the field of protein engineering. The yeast display technique was first published by the laboratory of Professor K. Dane Wittrup. The technology was sold to Abbott Laboratories in 2001....

.

Fluorescein can also be conjugated to nucleoside triphosphate
Nucleoside triphosphate
Nucleoside triphosphate is a nucleoside with three phosphates. Natural nucleoside triphosphates include adenosine triphosphate , guanosine triphosphate , cytidine triphosphate , 5-methyluridine triphosphate , and uridine triphosphate . These terms refer to those nucleoside triphosphates that...

s and incorporated into a probe
Hybridization probe
In molecular biology, a hybridization probe is a fragment of DNA or RNA of variable length , which is used in DNA or RNA samples to detect the presence of nucleotide sequences that are complementary to the sequence in the probe...

 enzymatically for in situ hybridisation. The use of fluorescein amidite shown above allows one to synthesize
Oligonucleotide synthesis
Oligonucleotide synthesis is the chemical synthesis of relatively short fragments of nucleic acids with defined chemical structure . The technique is extremely useful in current laboratory practice because it provides a rapid and inexpensive access to custom-made oligonucleotides of the desired...

 labeled oligonucleotide
Oligonucleotide
An oligonucleotide is a short nucleic acid polymer, typically with fifty or fewer bases. Although they can be formed by bond cleavage of longer segments, they are now more commonly synthesized, in a sequence-specific manner, from individual nucleoside phosphoramidites...

s for the same purpose. Yet another technique termed molecular beacon
Molecular beacon
Molecular beacons are oligonucleotide hybridization probes that can report the presence of specific nucleic acids in homogenous solutions. The terms more often used is molecular beacon probes. Molecular beacons are hairpin shaped molecules with an internally quenched fluorophore whose fluorescence...

s makes use of synthetic fluorescein-labeled oligonucleotides. Fluorescein-labelled probes can be imaged using FISH
Fluorescent in situ hybridization
FISH is a cytogenetic technique developed by biomedical researchers in the early 1980s that is used to detect and localize the presence or absence of specific DNA sequences on chromosomes. FISH uses fluorescent probes that bind to only those parts of the chromosome with which they show a high...

, or targeted by antibodies using immunohistochemistry
Immunohistochemistry
Immunohistochemistry or IHC refers to the process of detecting antigens in cells of a tissue section by exploiting the principle of antibodies binding specifically to antigens in biological tissues. IHC takes its name from the roots "immuno," in reference to antibodies used in the procedure, and...

. The latter is a common alternative to digoxigenin
Digoxigenin
Digoxigenin is a steroid found exclusively in the flowers and leaves of the plants Digitalis purpurea, Digitalis orientalis and Digitalis lanata , where it is attached to sugars, to form the glycosides Digoxigenin (DIG) is a steroid found exclusively in the flowers and leaves of the plants...

, and the two are used together for labelling two genes in one sample.

Health care applications

"Fluorescein sodium", the sodium salt of fluorescein, is used extensively as a diagnostic tool in the field of ophthalmology
Ophthalmology
Ophthalmology is the branch of medicine that deals with the anatomy, physiology and diseases of the eye. An ophthalmologist is a specialist in medical and surgical eye problems...

 and optometry
Optometry
Optometry is a health care profession concerned with eyes and related structures, as well as vision, visual systems, and vision information processing in humans. Optometrists, or Doctors of Optometry, are state licensed medical professionals trained to prescribe and fit lenses to improve vision,...

, where topical fluorescein is used in the diagnosis of corneal abrasion
Corneal abrasion
Corneal abrasion is a medical condition involving the loss of the surface epithelial layer of the eye's cornea.-Symptoms and signs:Symptoms of corneal abrasion include pain, photophobia, a foreign-body sensation, excessive squinting, and a reflex production of tears...

s, corneal ulcer
Corneal ulcer
A corneal ulcer, or ulcerative keratitis, is an inflammatory condition of the cornea involving loss of its outer layer. It is very common in dogs and is sometimes seen in cats...

s and herpetic corneal infections. It is also used in rigid gas permeable
Rigid gas permeable
Rigid gas permeable lenses are rigid contact lenses made of oxygen-permeable polymers. Initially developed in the late 1970s, and through the 1980s and 1990s, they were an improvement over prior 'hard' lenses that restricted oxygen transmission to the eye....

 contact lens fitting to evaluate the tear layer under the lens. It is available as sterile single-use sachets containing lint-free paper applicators soaked in fluorescein sodium.

Intravenous or oral fluorescein is used in fluorescein angiography
Fluorescein angiography
Intravenous Fluorescein angiography or fluorescent angiography is a technique for examining the circulation of the retina using the dye tracing method...

 in research and to diagnose and categorize vascular disorders in e.g. legs, including retinal disease macular degeneration
Macular degeneration
Age-related macular degeneration is a medical condition which usually affects older adults and results in a loss of vision in the center of the visual field because of damage to the retina. It occurs in “dry” and “wet” forms. It is a major cause of blindness and visual impairment in older adults...

, diabetic retinopathy
Diabetic retinopathy
Diabetic retinopathy is retinopathy caused by complications of diabetes mellitus, which can eventually lead to blindness....

, inflammatory intraocular conditions, and intraocular tumor
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...

s , and, increasingly, during surgery for brain tumor
Brain tumor
A brain tumor is an intracranial solid neoplasm, a tumor within the brain or the central spinal canal.Brain tumors include all tumors inside the cranium or in the central spinal canal...

s.

Air Sea Rescue

During World War 2, German aircrew carried small containers of fluorescein. In the event of parachuting into the sea after being being shot down, the dye would be released into the water. This produced a vivid marking that could be seen from the air over long distances and aided the Air-sea rescue
Air-sea rescue
Air-sea rescue is the coordinated search and rescue of the survivors of emergency water landings as well as people who have survived the loss of their sea-going vessel. ASR can involve a wide variety of resources including seaplanes, helicopters, submarines, rescue boats and ships...

 of the downed crew. This was later adopted by other air forces.

Uses in river systems

One of its more recognizable uses was in the Chicago River
Chicago River
The Chicago River is a system of rivers and canals with a combined length of that runs through the city of the same name, including its center . Though not especially long, the river is notable for being the reason why Chicago became an important location, as the link between the Great Lakes and...

, where fluorescein was the first substance used to dye the river green on St. Patrick's Day in 1962. In 1966, environmentalists forced a change to a vegetable-based dye to protect local wildlife.

Other uses of fluorescein include using it as a water-soluble dye added to rainwater in environmental testing simulations to aid in locating and analyzing any water leaks, and in Australia and New Zealand as a methylated spirit
Methylated spirit
Denatured alcohol or methylated spirits is ethanol that has additives to make it more poisonous or unpalatable, and thus, undrinkable. In some cases it is also dyed....

 dye.

Oilfield application

Fluorescein dye solutions, typically 15% active, are commonly used as an aid to leak detection during hydrostatic test
Hydrostatic test
A hydrostatic test is a way in which leaks can be found in pressure vessels such as pipelines and plumbing. The test involves placing water, which is often dyed for visibility, in the pipe or vessel at the required pressure to ensure that it will not leak or be damaged. It is the most common method...

ing of subsea oil and gas
Petroleum
Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...

 pipelines
Pipeline transport
Pipeline transport is the transportation of goods through a pipe. Most commonly, liquids and gases are sent, but pneumatic tubes that transport solid capsules using compressed air are also used....

 and other subsea infrastructure. Leaks can be detected by divers carrying ultraviolet lights.

Safety

Topical, oral, and intravenous use of fluorescein can cause adverse reaction
Adverse effect (medicine)
In medicine, an adverse effect is a harmful and undesired effect resulting from a medication or other intervention such as surgery.An adverse effect may be termed a "side effect", when judged to be secondary to a main or therapeutic effect. If it results from an unsuitable or incorrect dosage or...

s, including nausea
Nausea
Nausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...

, vomiting
Vomiting
Vomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose...

, hives
Urticaria
Urticaria is a kind of skin rash notable for pale red, raised, itchy bumps. Hives is frequently caused by allergic reactions; however, there are many non-allergic causes...

, acute
Acute (medicine)
In medicine, an acute disease is a disease with either or both of:# a rapid onset, as in acute infection# a short course ....

 hypotension
Hypotension
In physiology and medicine, hypotension is abnormally low blood pressure, especially in the arteries of the systemic circulation. It is best understood as a physiologic state, rather than a disease. It is often associated with shock, though not necessarily indicative of it. Hypotension is the...

, anaphylaxis
Anaphylaxis
Anaphylaxis is defined as "a serious allergic reaction that is rapid in onset and may cause death". It typically results in a number of symptoms including throat swelling, an itchy rash, and low blood pressure...

 and related anaphylactoid reaction
Anaphylaxis
Anaphylaxis is defined as "a serious allergic reaction that is rapid in onset and may cause death". It typically results in a number of symptoms including throat swelling, an itchy rash, and low blood pressure...

, causing cardiac arrest
Cardiac arrest
Cardiac arrest, is the cessation of normal circulation of the blood due to failure of the heart to contract effectively...

 and sudden death due to anaphylactic shock.

The most common adverse reaction is nausea, due to a difference in the pH from the body and the pH of the sodium fluorescein dye; a number of other factors, however, are considered contributors as well. The nausea usually is transient and subsides quickly. Hives can range from a minor annoyance to severe, and a single dose of antihistamine may give complete relief. Anaphylactic shock and subsequent cardiac arrest and sudden death are very rare, but because they occur within minutes, a health care provider who uses fluorescein should be prepared to perform emergency resuscitation.

Intravenous use has the most reported adverse reactions, including sudden death, but this may reflect greater use rather than greater risk. Both oral and topical uses have been reported to cause anaphylaxis, including one case of anaphylaxis with cardiac arrest (resuscitated
Cardiopulmonary resuscitation
Cardiopulmonary resuscitation is an emergency procedure which is performed in an effort to manually preserve intact brain function until further measures are taken to restore spontaneous blood circulation and breathing in a person in cardiac arrest. It is indicated in those who are unresponsive...

) following topical use in an eye drop. Reported rates of adverse reactions vary from 1% to 6%. The higher rates may reflect study populations that include a higher percentage of persons with prior adverse reactions. The risk of an adverse reaction is 25 times higher if the person has had a prior adverse reaction. The risk can be reduced with prior (prophylactic) use of antihistamine
Antihistamine
An H1 antagonist is a histamine antagonist of the H1 receptor that serves to reduce or eliminate effects mediated by histamine, an endogenous chemical mediator released during allergic reactions...

s
and prompt emergency management of any ensuing anaphylaxis. A simple prick test may help to identify persons at greatest risk of adverse reaction.

See also

  • Chemical derivatives of fluorescein:
    • Eosin
      Eosin
      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....

    • Carboxyfluorescein
      Carboxyfluorescein
      Carboxyfluorescein refers to two fluorescent dyes with an excitation and emission of 492/517 nm, respectively. They are commonly used as a tracer agents. The dyes are membrane-impermeant and can be loaded into cells by microinjection or scrape loading. It can be incorporated into liposomes,...

    • Fluorescein isothiocyanate
      Fluorescein isothiocyanate
      Fluorescein isothiocyanate is a derivative of fluorescein used in wide-ranging applications including flow cytometry. FITC is the original fluorescein molecule functionalized with an isothiocyanate reactive group , replacing a hydrogen atom on the bottom ring of the structure...

       (FITC)
    • Fluorescein amidite
      Fluorescein amidite
      Fluorescein amidite, abbreviated as FAM , is an important synthetic equivalent of fluorescein dye used in oligonucleotide synthesis and molecular biology...

       (FAM)
    • Erythrosine
      Erythrosine
      Erythrosine, also known as Red No. 3, is an organoiodine compound, specifically a derivative of fluorone. It is cherry-pink synthetic, primarily used for food coloring. It is the disodium salt of 2,4,5,7-tetraiodofluorescein...

    • Rose Bengal
      Rose bengal
      Rose Bengal is a stain. Its sodium salt is commonly used in eye drops to stain damaged conjunctival and corneal cells and thereby identify damage to the eye...

    • DyLight Fluor
      DyLight Fluor
      The DyLight Fluor family of fluorescent dyes are produced by Dyomics in collaboration with Thermo Fisher Scientific. DyLight dyes are typically used in biotechnology and research applications as biomolecule, cell and tissue labels for fluorescence microscopy, cell biology or molecular...

      , a product line of fluorescent dyes
  • Fluorescein diacetate hydrolysis
    Fluorescein diacetate hydrolysis
    Fluorescein diacetate hydrolysis assays can be used to measure enzyme activity produced by microbes in a sample. A bright yellow glow is produced and is strongest when enzymatic activity is greatest...

    , a biochemistry laboratory test
  • Other dyes:
    • Methylene blue
      Methylene blue
      Methylene blue is a heterocyclic aromatic chemical compound with the molecular formula C16H18N3SCl. It has many uses in a range of different fields, such as biology and chemistry. At room temperature it appears as a solid, odorless, dark green powder, that yields a blue solution when dissolved in...

    • Laser dye
      Laser dye
      Laser dyes are very large organic molecules with molecular weights of a few hundred mu. When one of these organic molecules is dissolved in a suitable liquid solvent it can be used as gain medium in a dye laser. Laser dye solutions absorb at shorter wavelengths end emit at longer wavelengths...

      s

External links

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