The intense green color of the cation results from a strong absorption band at 621 nm (extinction coefficient of 105 M−1 cm−1).

The leuco form of malachite green was first prepared by Hermann Fischer in 1877 by condensing benzaldehyde and dimethylaniline in the molecular ratio 1:2 in the presence of sulfuric acid.

Anyone handling the contaminated money will find that on upon washing the hands, a green stain on the skin that lasts for several days will result.

[6] A set of malachite green derivatives is also a key component in a fluorescence microscopy tool called the fluorogen activating protein/fluorogen system.

In 1992, Canadian authorities determined that eating fish contaminated with malachite green posed a significant health risk.

Due to its low manufacturing cost, malachite green is still used in certain countries with less restrictive laws for non aquaculture purposes.

In 2005, analysts in Hong Kong found traces of malachite green in eels and fish imported from China.

In 2006, the United States Food and Drug Administration (FDA) detected malachite green in seafood from China, among others, where the substance is also banned for use in aquaculture.

[9] In June 2007, the FDA blocked the importation of several varieties of seafood due to continued malachite green contamination.

[citation needed] Rats fed malachite green experience "a dose-related increase in liver DNA adducts" along with lung adenomas.

During the experiment, rats were fed up to 543 ppm of leucomalachite green, an extreme amount compared to the average 5 ppb discovered in fish.

After a period of two years, an increase in lung adenomas in male rats was discovered but no incidences of liver tumors.