Last updated on: 3/18/2020 | Author:

An estimated 26 million animals are used every year in the United States for scientific and commercial testing. Animals are used to develop medical treatments, determine the toxicity of medications, check the safety of products destined for human use, and other biomedical, commercial, and health care uses. Research on living animals has been practiced since at least 500 BC.

Proponents of animal testing say that it has enabled the development of many life-saving treatments for both humans and animals, that there is no alternative method for researching a complete living organism, and that strict regulations prevent the mistreatment of animals in laboratories.

Opponents of animal testing say that it is cruel and inhumane to experiment on animals, that alternative methods available to researchers can replace animal testing, and that animals are so different from human beings that research on animals often yields irrelevant results. Read more background…


Pro & Con Arguments

Pro 1

Animal testing contributes to life-saving cures and treatments.

The California Biomedical Research Association states that nearly every medical breakthrough in the last 100 years has resulted directly from research using animals. [9] Animal research has contributed to major advances in treating conditions such as breast cancer, brain injury, childhood leukemia, cystic fibrosis, multiple sclerosis, tuberculosis, and more, and was instrumental in the development of pacemakers, cardiac valve substitutes, and anesthetics. [10][11][12][13]

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Pro 2

Animal testing is crucial to ensure that vaccines are safe.

Scientists racing to develop a vaccine for coronavirus during the 2020 global pandemic need to test on genetically modified mice to ensure that the vaccine doesn’t make the virus worse. [133] [119] Nikolai Petrovsky, professor in the College of Medicine and Public Health at Flinders University in Australia, said testing a coronavirus vaccine on animals is “absolutely essential” and skipping that step would be “fraught with difficulty and danger.” [133]

Researchers have to test extensively to prevent “vaccine enhancement,” a situation in which a vaccine actually makes the disease worse in some people. [141] Peter Hotez, Dean for the National School of Tropical Medicine at Baylor College, said, “The way you reduce that risk is first you show it does not occur in laboratory animals.” [119]

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Pro 3

There is no adequate alternative to testing on a living, whole-body system.

A living systems, human beings and animals are extremely complex. Studying cell cultures in a petri dish, while sometimes useful, does not provide the opportunity to study interrelated processes occurring in the central nervous system, endocrine system, and immune system. [9] Evaluating a drug for side effects requires a circulatory system to carry the medicine to different organs. [15]

Conditions such as blindness and high blood pressure cannot be studied in tissue cultures. [9] Even the most powerful supercomputers are unable to accurately simulate the workings of the human brain’s 100 billion interconnected nerve cells. [132]

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Pro 4

Animals are appropriate research subjects because they are similar to human beings in many ways.

Chimpanzees share 99% of their DNA with humans, and mice are 98% genetically similar to humans. [9] All mammals, including humans, are descended from common ancestors, and all have the same set of organs (heart, kidneys, lungs, etc.) that function in essentially the same way with the help of a bloodstream and central nervous system. [17] Because animals and humans are so biologically similar, they are susceptible to many of the same conditions and illnesses, including heart disease, cancer, and diabetes. [18]

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Pro 5

Animals must be used in cases when ethical considerations prevent the use of human subjects.

When testing medicines for potential toxicity, the lives of human volunteers should not be put in danger unnecessarily. It would be unethical to perform invasive experimental procedures on human beings before the methods have been tested on animals, and some experiments involve genetic manipulation that would be unacceptable to impose on human subjects before animal testing. [19] The World Medical Association Declaration of Helsinki states that human trials should be preceded by tests on animals. [20]

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Pro 6

Animals themselves benefit from the results of animal testing.

Vaccines tested on animals have saved millions of animals that would otherwise have died from rabies, distemper, feline leukemia, infectious hepatitis virus, tetanus, anthrax, and canine parvo virus. Treatments for animals developed using animal testing also include pacemakers for heart disease and remedies for glaucoma and hip dysplasia. [9][21]

Animal testing has been instrumental in saving endangered species from extinction, including the black-footed ferret, the California condor and the tamarins of Brazil. [13][9] The American Veterinary Medical Association (AVMA) endorses animal testing to develop safe drugs, vaccines, and medical devices. [23]

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Pro 7

Animal research is highly regulated, with laws in place to protect animals from mistreatment.

In addition to local and state laws and guidelines, animal research has been regulated by the federal Animal Welfare Act (AWA) since 1966. As well as stipulating minimum housing standards for research animals (enclosure size, temperature, access to clean food and water, and others), the AWA also requires regular inspections by veterinarians. [3]

All proposals to use animals for research must be approved by an Institutional Animal Care and Use Committee (IACUC) set up by each research facility. Most major research institutions’ programs are voluntarily reviewed for humane practices by the Association for Assessment and Accreditation of Laboratory Animal Care International (AAALAC). [24][25]

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Pro 8

Animals often make better research subjects than human beings because of their shorter life cycles.

Laboratory mice, for example, live for only two to three years, so researchers can study the effects of treatments or genetic manipulation over a whole lifespan, or across several generations, which would be infeasible using human subjects. [29][9] Mice and rats are particularly well-suited to long-term cancer research, partly because of their short lifespans. [30]

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Pro 9

Animal researchers treat animals humanely, both for the animals’ sake and to ensure reliable test results.

Research animals are cared for by veterinarians, husbandry specialists, and animal health technicians to ensure their well-being and more accurate findings. Rachel Rubino, attending veterinarian and director of the animal facility at Cold Springs Harbor Laboratory, said, “Most people who work with research animals love those animals… We want to give them the best lives possible, treat them humanely.” [28] At Cedars-Sinai Medical Center’s animal research facility, dogs are given exercise breaks twice daily to socialize with their caretakers and other dogs, and a “toy rotation program” provides opportunities for play. [32]

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Pro 10

Animals do not have rights, therefore it is acceptable to experiment on them.

Animals do not have the cognitive ability or moral judgment that humans do and because of this they have been treated differently than humans by nearly every culture throughout recorded history. If we granted animals rights, all humans would have to become vegetarians, and hunting would need to be outlawed. [33][34]

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Pro 11

The vast majority of biologists and several of the largest biomedical and health organizations in the United States endorse animal testing.

A poll of 3,748 scientists by the Pew Research Center found that 89% favored the use of animals in scientific research. [120] The American Cancer Society, American Physiological Society, National Association for Biomedical Research, American Heart Association, and the Society of Toxicology all advocate the use of animals in scientific research. [36][37][38][39][40]

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Pro 12

Some cosmetics and health care products must be tested on animals to ensure their safety.

American women use an average of 12 personal care products per day, so product safety is of great importance. [41] The US Food and Drug Administration endorses the use of animal tests on cosmetics to “assure the safety of a product or ingredient.” [42] China requires that most cosmetics be tested on animals before they go on sale, so cosmetics companies must have their products tested on animals if they want distribution in one of the largest markets in the world. [43] Manufacturers of products such as hand sanitizer and insect repellent, which can protect people from Zika, malaria, and West Nile Virus, test on animals to meet legal requirements for putting these products on the market. [44]

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Con 1

Animal testing is cruel and inhumane.

According to Humane Society International, animals used in experiments are commonly subjected to force feeding, food and water deprivation, the infliction of burns and other wounds to study the healing process, the infliction of pain to study its effects and remedies, and “killing by carbon dioxide asphyxiation, neck-breaking, decapitation, or other means.” [47] The US Department of Agriculture reported in Jan. 2020 that research facilities used over 300,000 animals in activities involving pain in just one year. [102]

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Con 2

Scientists are able to test vaccines on humans volunteers.

Unlike animals used for research, humans are able to give consent to be used in testing and are a viable option when the need arises. [142] The COVID-19 (coronavirus) global pandemic demonstrated that researchers can skip animal testing and go straight to observing how vaccines work in humans. One company working on a COVID-19 vaccine, Moderna Therapeutics, worked on developing a vaccine using new technology: instead of being based on a weakened form of the virus, it was developed using a synthetic copy of the COVID-19 genetic code. [143]

Because the company didn’t take the traditional path of isolating live samples of a virus, it was able to fast-track the development process. [144] Tal Zaks, chief medical officer at Moderna, said, “I don’t think proving this in an animal model is on the critical path to getting this to a clinical trial.” [145]

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Con 3

Alternative testing methods now exist that can replace the need for animals.

Other research methods such as in vitro testing (tests done on human cells or tissue in a petri dish) offer opportunities to reduce or replace animal testing. [15] Technological advancements in 3D printing allow the possibility for tissue bioprinting: a French company is working to bioprint a liver that can test the toxicity of a drug. [16] Artificial human skin, such as the commercially available products EpiDerm and ThinCert, can be made from sheets of human skin cells grown in test tubes or plastic wells and may produce more useful results than testing chemicals on animal skin. [15][50][51]

The Environmental Protection Agency is so confident in alternatives that the agency intends to reduce chemical testing on mammals 30% by 2025 and end it altogether by 2035. [134] Humane Society International found that animal tests were more expensive than in vitro (testing performed outside of living organisms) in every scenario studied. [61]

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Con 4

Animals are very different from human beings and therefore make poor test subjects.

The anatomic, metabolic, and cellular differences between animals and people make animals poor models for human beings. [52] Paul Furlong, Professor of Clinical Neuroimaging at Aston University (UK), states that “it’s very hard to create an animal model that even equates closely to what we’re trying to achieve in the human.” [53] Thomas Hartung, Professor of evidence-based toxicology at Johns Hopkins University, argues for alternatives to animal testing because “we are not 70 kg rats.” [54]

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Con 5

Drugs that pass animal tests are not necessarily safe.

The 1950s sleeping pill thalidomide, which caused 10,000 babies to be born with severe deformities, was tested on animals prior to its commercial release. [5] Later tests on pregnant mice, rats, guinea pigs, cats, and hamsters did not result in birth defects unless the drug was administered at extremely high doses. [109][110] Animal tests on the arthritis drug Vioxx showed that it had a protective effect on the hearts of mice, yet the drug went on to cause more than 27,000 heart attacks and sudden cardiac deaths before being pulled from the market. [55][56]

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Con 6

Animal tests may mislead researchers into ignoring potential cures and treatments.

Some chemicals that are ineffective on (or harmful to) animals prove valuable when used by humans. Aspirin, for example, is dangerous for some animal species. [105] Intravenous vitamin C has shown to be effective in treating sepsis in humans, but makes no difference to mice. [127] Fk-506 (tacrolimus), used to lower the risk of organ transplant rejection, was “almost shelved” because of animal test results, according to neurologist Aysha Akhtar. [105] A report on stated that a “source of human suffering may be the dozens of promising drugs that get shelved when they cause problems in animals that may not be relevant for humans.” [106]

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Con 7

Only 5% of animals used in experiments are protected by US law.

The Animal Welfare Act (AWA) does not apply to rats, mice, fish, and birds, which account for 95% of the animals used in research. [28] The types of animals covered by the AWA account for fewer than one million animals used in research facilities each year, which leaves around 25 million other animals without protection from mistreatment. [1][2][26][102] [135] The US Department of Agriculture, which inspects facilities for AWA compliance, compiles annual statistics on animal testing but they only include data on the small percentage of animals subject to the Act. [135]

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Con 8

Animal tests do not reliably predict results in human beings.

94% of drugs that pass animal tests fail in human clinical trials. [57] According to neurologist Aysha Akhtar, MD, MPH, over 100 stroke drugs that were effective when tested on animals have failed in humans, and over 85 HIV vaccines failed in humans after working well in non-human primates. [58] A study published in Proceedings of the National Academy of Sciences of the United States of America (PNAS) found that nearly 150 clinical trials (human tests) of treatments to reduce inflammation in critically ill patients have been undertaken, and all of them failed, despite being successful in animal tests. [59][58]

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Con 9

There is increasing demand for cruelty-free products.

More than one-third of women only buy cosmetics from brands that do not use animal testing. [136] The market for cruelty-free cosmetics (products not tested on animals) is estimated to reach $10 billion by 2024. [137] At least 37 countries have banned or restricted the sale of cosmetics with ingredients tested on animals, including nations in the European Union. [138] In the US, California became the first state to make it illegal to sell most cosmetics that underwent animal testing. [139]

Michael Bachelor, Senior Scientist and Product Manager at biotech company MatTek, stated, “We can now create a model from human skin cells — keratinocytes — and produce normal skin or even a model that mimics a skin disease like psoriasis. Or we can use human pigment-producing cells — melanocytes — to create a pigmented skin model that is similar to human skin from different ethnicities. You can’t do that on a mouse or a rabbit.” [140]

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Con 10

Most experiments involving animals are flawed, wasting the lives of the animal subjects.

A peer-reviewed study found serious flaws in the majority of publicly funded US and UK animal studies using rodents and primates: “only 59% of the studies stated the hypothesis or objective of the study and the number and characteristics of the animals used.” [64] A 2017 study found further flaws in animal studies, including “incorrect data interpretation, unforeseen technical issues, incorrectly constituted (or absent) control groups, selective data reporting, inadequate or varying software systems, and blatant fraud.” [128]

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Con 11

The Animal Welfare Act has not succeeded in preventing horrific cases of animal abuse in research laboratories.

Violations of the Animal Welfare Act at the federally funded New Iberia Research Center (NIRC) in Louisiana included maltreatment of primates who were suffering such severe psychological stress that they engaged in self-mutilation, infant primates awake and alert during painful experiments, and chimpanzees being intimidated and shot with a dart gun. [68]

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Con 12

Medical breakthroughs involving animal research may still have been made without the use of animals.

Devoting enough money and resources to animal-free alternatives could result in the same medical advances achieved through animal testing. [107] [129] [130] Humane Research Australia (HRA) reports that many discoveries made by non-animal methods were later verified by animal experiments, “giving false credit” to animal use. [130]

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Did You Know?
1. 95% of animals used in experiments are not protected by the federal Animal Welfare Act (AWA), which excludes birds, rats and mice bred for research, and cold-blooded animals such as reptiles and most fish. [1] [2] [3]
2. 89% of scientists surveyed by the Pew Research Center were in favor of animal testing for scientific research. [120]
3. Chimpanzees share 99% of their DNA with humans, and mice are 98% genetically similar to humans. The US National Institutes of Health announced it would retire its remaining 50 research chimpanzees to the Federal Chimpanzee Sanctuary System in 2015, leaving Gabon as the only country to still experiment on chimps. [4] [117]
4. A Jan. 2020 report from the USDA showed that in one year of research, California used more cats (1,682) for testing than any other state. Ohio used the most guinea pigs (35,206), and Massachusetts used the most dogs (6,771) and primates (11,795). [102]
5. Researchers Joseph and Charles Vacanti grew a human "ear" seeded from implanted cow cartilage cells on the back of a living mouse to explore the possibility of fabricating body parts for plastic and reconstructive surgery. [108]


Our Latest Updates (archived after 30 days)

Animal Import Ban from China Threatens US COVID-19 Vaccine Development
2/24/2021 -

A shortage of monkeys, including pink-faced rhesus macaques, threatened vaccine development at the beginning of the pandemic and as variants of COVID-19 were found. The monkeys were previously flown in from China, but a ban on wildlife imports from China forced researchers to look elsewhere, a difficult task as China previously supplied over 60% of research monkeys in the United States.

Archived Notices (archived after 30 days)