Crystal violet or Gentian violet (also known as Methyl Violet 10B, hexamethyl pararosaniline chloride, or pyoctanin(e)) is a triarylmethane dye. The dye is used as a histological stain and in Gram’s method of classifying bacteria. Crystal violet has antibacterial, antifungal, and anthelmintic properties and was formerly important as a topical antiseptic. The medical use of the dye has been largely superseded by more modern drugs, although it is still listed by the World Health Organization.
The name "gentian violet" was originally used for a mixture of methyl pararosaniline dyes (methyl violet) but is now often considered a synonym for crystal violet. The name refers to its colour, being like that of the petals of a gentian flower; it is not made from gentians or from violets.
Bacteria stained with crystal violet.
Crystal violet is not used as a textile dye. Instead it is used to dye paper and as a component of navy blue and black inks for printing, ball-point pens and ink-jet printers. It is also used to colourize diverse products such as fertilizers, anti-freezes, detergents, and leather jackets.
The dye is also used as a histological stain, particularly in Gram's method for classifying bacteria.
When conducting DNA gel electrophoresis, crystal violet can be used as a non-toxic DNA stain as an alternative to fluorescent, intercalating dyes such as ethidium bromide. Used in this manner it may be either incorporated into the agarose gel or applied after the electrophoresis process is finished. Used at a 0.001% concentration and allowed to stain a gel after electrophoresis for 30 minutes, it can detect as little as 16ng of DNA. Through use of a methyl orange counterstain and a more complex staining method, sensitivity can be improved further to 8ng of DNA. When crystal violet is used as an alternative to fluorescent stains, it is not necessary to use ultraviolet illumination; this has made crystal violet popular as a means of avoiding UV-induced DNA destruction when performing DNA cloning in vitro.
Gentian violet has antibacterial, antifungal, and anthelmintic properties. It is used medically for these properties, in particular for dentistry, and is also known as "pyoctanin" (or "pyoctanine"). It is commonly used for:
Marking the skin for surgery preparation and allergy testing
Tinea; e.g. Athlete's foot, jock itch, and ringworm
Candida albicans and related infections; e.g. thrush, yeast infections
Impetigo, used primarily before the advent of antibiotics, but still useful to persons who may be allergic to penicillin, as it cleans the open sores and prevents spread of the contagion
Abrasion; It has also one of the best agents for "scabbing" up an abrasion or "strawberry" type of weeping wound where the flesh is abraded away. It will prevent infection in almost any wound or burn and quickly help the epithelium form a scab. It does not burn when applied and temporary skin discoloration is a minor side effect.
In forensics, gentian violet was used to develop fingerprints. Crystal violet is also used as a tissue stain in the preparation of light microscopy sections.
In laboratory, solutions containing crystal violet and formalin are often used to simultaneously fix and stain cells grown in tissue culture to preserve them and make them easily visible, since most cells are colourless. It is also sometimes used as a cheap way to put identification markings on laboratory mice since many strains of lab mice are albino so the purple colour stays on their fur for several weeks.
In body piercing, gentian violet is commonly used to mark the location for placing piercings, including surface piercings.
Gentian violet was once used as antiseptic for Singaporean prisoners who received caning. The solution was applied after the procedure.
Crystal violet is one of the components of methyl violet, a dye that was first synthesized by Charles Lauth in 1861. From 1866, methyl violet was manufactured by the Saint-Denis based firm of Poirrier et Chappat and marketed under the name "Violet de Paris". It was a mixture of the tetra-, penta- and hexamethylated pararosanilines.
Crystal violet itself was first synthesized in 1883 by Alfred Kern (1850–1893) working in Basel at the firm of Bindschedler and Busch. To optimize the difficult synthesis which used the toxic gas phosgene (carbonyl chloride), Kern entered into a collaboration with the German chemist Heinrich Caro at BASF. Kern also found that by starting with diethylaniline rather than dimethylaniline he could synthesize the closely related violet dye now known as C.I. 42600 or C.I. Basic violet 4.
The name "gentian violet" (or Gentianaviolett in German) is thought to have been introduced by the German pharmacist George Grübler who in 1880 created a company in Leipzig that specialized in the sale of staining reagents for histology. The gentian violet stain marketed by Grübler probably contained a mixture of methylated pararosaniline dyes. The stain proved popular and in 1884 was used by Hans Christian Gram to stain bacteria. He credited Paul Ehrlich for the aniline-gentian violet mixture. Grübler's gentian violet was probably very similar, if not identical, to Lauth’s methyl violet which had been used as a stain by Victor André Cornil in 1875.
Although the name gentian violet continued to be used for the histological stain, the name was not used in the dye and textile industries. The composition of the stain was not defined and different suppliers used different mixtures. In 1922 the Biological Stain Commission appointed a committee chaired by Harold Conn to look into the suitability of the different commercial products. In his book Biological Stains Conn describes gentian violet as a "poorly defined mixture of violet rosanilins".
The German ophthalmologist Jakob Stilling is credited with discovering the antiseptic properties of gentian violet. He published a monograph in 1890 on the bactericidal effects of a solution that he christened "pyoktanin" which was probably a mixture of aniline dyes similar to gentian violet. He set up a collaboration with E. Merck & Co. to market "Pyoktanin caeruleum" as an antiseptic.
In 1902, Drigalski and Conradi found that although crystal violet inhibited the growth of many bacteria, it has little effect on Bacillus coli (Escherichia coli) and Bacillus typhi (Salmonella typhi), which are both Gram-negative bacteria. A much more detailed study of the effects of Grübler’s gentian violet on different strains of bacteria was published by John Churchman in 1912. He found that most Gram-positive bacteria were sensitive to the dye while most Gram-negative bacteria were not and observed that the dye tended to act as a bacteriostatic agent rather than a bactericide.
One study in mice demonstrated dose-related carcinogenic potential at several different organ sites. The Food and Drug Administration in the US has determined that gentian violet has not been shown by adequate scientific data to be safe for use in animal feed. Use of gentian violet in animal feed causes the feed to be adulterated and is a violation of the Federal Food, Drug, and Cosmetic Act in the US. On June 28, 2007, the US food and Drug Administration issued an "import alert" on farm raised seafood from China because unapproved antimicrobials, including gentian violet, had been consistently found in the products. The FDA report states:
"Like MG [malachite green], CV [crystal violet] is readily absorbed into fish tissue from water exposure and is reduced metabolically by fish to the leuco moiety, leucocrystal violet (LCV). Several studies by the National Toxicology Program reported that the carcinogenic and mutagenic effects of crystal violet in rodents. It has also been linked to increased risk of human bladder cancer. The leuco form induces renal, hepatic and lung tumor in mice."
Gentian violet's common side effect is the staining of skin and cloth, but it can easily be washed off skin with a solution of bleach and water. However, if used on ulcerations or open wounds it can cause tattooing. It is generally considered safe for use on children and breastfeeding mothers. It has even been applied to the mouth and lips of premature infants, and has a long history of safe use. La Leche League recommends gentian violet for thrush on the nipple. However, in large quantities, gentian violet may lead to ulceration of a baby's mouth and throat and is linked with mouth cancer. Gentian violet has also been linked to cancer in the digestive tract of other animals.