Mascara is a mild irritant, and rabbits have, historically, been used to test how much discomfort new products can cause.
However, a cheaper and more reliable test is now being developed by scientists at the University of Liverpool, UK, involving miniscule protozoa.
"This will remove animal cruelty from the equation," researchers said.
The scientists were able to examine potential toxicity caused by mascara, based on the growth of the protozoa when placed in experimental chambers containing the cosmetic.
Six different brands of mascara were tested, by painting it on small glass plates and placing these in the chambers. The protozoa and their food were then added.
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There was a substantial difference between brands, with some killing the protozoa and others not harming them at all.
"This test has great potential for reducing the use of rabbits as it is both cheap and reliable, and while the protozoa have a similar metabolism to animals they are not classed as such," Dr David Montagnes, who supervised the project said.
"When you can develop a simpler and cheaper alternative, there is really no need to test cosmetics on animals," said Montagnes.
The study was published in the Journal of Cosmetic Sciences.