Explainer: What Is Animal Testing?

Vaccines, medications and cosmetics rely on animal testing even though the process is cruel, unreliable and often inaccurate.

Jo-Anne McArthur / The Ghosts In Our Machine / We Animals Media

Explainer Animal Testing Policy

The use of animals in experiments is so endemic that “guinea pig” is used as an alternative term for “test subject.” But underlying this ubiquity is a set of processes that harm animals unnecessarily: rats force-fed drugs designed to induce tumors, monkeys kept in tiny cages with chemicals irritating their skin and beagles euthanized without any anesthesia.

Critics say many of these experiments are unreliable and even unnecessary. Advocates for reduced animal testing earned a win in December 2022: the FDA announced that it would no longer require animal tests prior to approving a drug for human trials.

What Is Animal Testing?

Animal testing, sometimes called in vivo testing, is a process of determining if certain medications, vaccines and cosmetics are safe for humans by first experimenting with them on animals. Animal testing is common in most countries and has been used in some forms throughout much of human history.

Cosmetic Testing

Cosmetic testing is a process of using animals to test any cosmetic product before human use, such as makeups, lotions, creams, fragrances, oils or facial masks. 

Testing for Medicine

Medical testing involves using animals to examine new drugs, research biological systems, investigate genetic factors, delve into animal psychologies or test out surgical strategies. Nowadays, drugs are the most common form of medical testing on animals.  

The History of Animal Testing

Animal testing is a long-documented practice, with some of the oldest instances dating back to around 300 B.C. in ancient Greece. Yet while animal testing was widespread in the form of vivisection and practice for operations, it wasn’t until the 20th century that medicines were commonly tested on animals. In fact, several laws were passed in this period, including the 1938 Federal Food, Drug, and Cosmetic Act in the U.S., that encouraged or mandated the use of animals in testing before human consumption. 

What Types of Animals Are Used in Animal Testing?


Common invertebrates used in animal testing include fruit flies and nematode worms. Unfortunately for these animals, no federal protections exist to minimize their pain or suffering in the U.S.


There’s truth in the common phrase “lab rat” — 95 percent of animals used in animal testing are mice or rats. Dogs, cats, pigs, monkeys, other primates, rabbits and sheep are all used in addition to rodents. 

How Many Animals Are Used in Experiments Each Year?

This is a difficult question to answer, because the U.S. Department of Agriculture only counts certain species of animals in its annual review of animal testing. Mice and rats specifically bred for testing purposes are not counted because they do not fall under the U.S. Animal Welfare Act.

However, it’s been estimated that at least 50 million animals are used in the U.S. every year. The real number is unknown and may be higher. Worldwide, exact numbers are unknown, but some estimate the number to be around 200 million experiments per year. 

What’s Wrong With Animal Testing?

Is Animal Testing Painful?

Some researchers attempt to reduce the pain for animal test subjects, but many do not. According to the USDA animal usage summary report, roughly 8 percent of animals were experimented on with no measures taken to ensure pain reduction. This report does not take into account animals that do not fall under the Animal Welfare Act, so the real number is unknowable and likely much higher. 

Even animals protected by the Animal Welfare Act are often subjected to levels of pain that are hard to comprehend. Of all surgeries on animals, 40 percent do not report using anesthesia, and drugs are often force-fed to animals. Animals are also often killed after the experiments are completed, long before the end of their natural lifespan.  

Are Animal Testing Results Reliable?

Animal tests do not catch all possible side effects before drugs move to a later phase of testing. According to a 2004 report from the USDA, 92 percent of medicines that pass an animal testing phase will not proceed to market, and a major cause of this failure is safety problems that were not predicted by animal tests. More recent reports from scientists estimate an even higher number of 96 percent

There are a variety of reasons why animal tests are considered unreliable. According to a 2015 review in the Cambridge Quarterly of Healthcare Ethics, these include the effects of laboratory conditions; the different ways that diseases impact animals and humans; and the differences in physiology and genetics across species, all of which lead to inaccuracies. Due to such factors, a breakthrough meta-analysis published in Alternatives to Laboratory Animals in 2015 argued that a lack of toxicity of a drug in any of the five species most commonly used in animal testing — dogs, rats, mice, rabbits and monkeys — was not able to indicate the likelihood of a similar lack of toxicity in humans. In other words, animal tests don’t work. 

Advocates for animal testing often argue that the complexity of a living organism — the organs, circulatory system and genetic regulation — will affect drugs in a way that single tissue samples cannot. This argument fails to account for the fact that nonhuman systems are very different from human systems, which leads to inaccuracy. 

Animal testing can also lead to banning drugs that would benefit humans. For example, tamoxifen, a drug used to treat breast cancer, can cause tumors in rodents. If this drug had been tested on animals in early phases of research, it is likely the benefits of tamoxifen would have remained untapped. 

Is Animal Testing Cruel?

Due to the combination of low accuracy and high amounts of pain, it is difficult to argue that animal testing is not cruel. Animals such as rats, mice, dogs and chimpanzees are burned, poisoned, crippled, starved or abused in other ways via drugs, confinement or other invasive procedures.

Animals like these are sensitive to pain, emotionally empathetic and capable of forming social bonds. But to the researchers in charge of them, they are nothing more than tools. 

Is Animal Testing Archaic?

Due to the inaccuracy of animal testing, voices have arisen to criticize its outdated methodology. Not only is animal testing an old-fashioned practice that hasn’t been brought into the 21st century, but evidence shows it is likely holding back medical research. 

Is Animal Testing Wasteful?

Because of the inaccuracy of animal testing, many scientists and experts argue that its existence is inherently wasteful. British doctor Ian Roberts writes that “biased or imprecise results from animal experiments may result in clinical trials of biologically inert or even harmful substances, thus . . . wasting scarce research resources.”

Is Animal Testing Illegal?

Cosmetics testing has been banned in 42 countries and 10 U.S. states (California, Hawaii, Illinois, Maine, Maryland, Nevada, New Jersey, Louisiana, New York and Virginia). New York’s ban on cosmetic testing goes into effect in January 2023, which makes it possible that more states will continue to follow their lead. 

No countries currently ban medical animal testing, but this may soon change. This year, Switzerland held a referendum on medical animal testing. A large Swiss pharmaceutical lobby campaigned against the initiative, which was ultimately unsuccessful. But the fact that animal testing went from untouchable fact to subject of a national debate sparks doubt about its continued acceptance in the future. 

Aren’t There Laws To Protect Animals Used in Experiments?

There do exist some laws to protect animals, such as the U.S. Animal Welfare Act. However, this law does very little to protect animals from pain, and doesn’t even count rats and mice as protected animals.

Cosmetic testing is far more controversial in the public sphere and therefore more heavily regulated. It is almost entirely banned in the European Union and other countries, including Guatemala, Colombia, India, Taiwan and the U.K. The U.S. has no federal cosmetics ban.

Why Are Animals Still Used in Experiments?

Despite the lack of sustained evidence for animal testing’s usefulness, and the possibility of cheaper alternatives (as discussed below), animal testing seems to be used far more often than it should be. Why?

First of all, the pharmaceutical industry has maintained a clear interest in preserving animal testing, and only very rarely review evidence about its actual usefulness. Another issue is scientific tradition and established practice. Scientists are likely to cite historical precedent as a reason for selecting an animal model, as opposed to the model’s similarity to human systems or effectiveness in predicting toxicity, according to a 2019 paper in Alternatives to Animal Experimentation

Should Animal Testing Be Banned?

Calls to ban animal testing because of its ineffectiveness and cruelty have been getting louder in recent years. Entire conferences are held to discuss alternatives to animal testing, and many petitions and campaigns are igniting across the world. These voices don’t just originate from the animal liberation movement, either. Prominent scientists, pharmaceutical bosses and concerned citizens are joining the chorus. 

Alternatives to Animal Testing

Thankfully, there exist several alternatives to animal testing, some of which have become more popular and common in recent years. 

In Vitro Testing

In vitro testing is a process of conducting an examination in a test tube using tissue samples.

Human Tissues

Real human tissue samples, which can be ethically donated to science as a result of surgeries or after death, are viable alternatives for testing localized drugs. For years, research has indicated that various in vitro methods can hypothetically outperform animal testing (and cost less too), although this form of testing is likely best used for understanding toxicity within a single organ or organ system, not the entire human body. 

A new human tissue testing method has emerged recently that shows promise. An in vitro skin testing model called h-CLAT recently entered use in Europe and Japan, paving the way for more techniques that don’t require animal experimentation. 

In Vitro Modeling Systems

Another form of in vitro testing involves a synthetic model that can replicate human systems. While less accurate, this method is cheaper and far easier to source, although it is best used for simpler human organs like the skin. One example, the EpiDerm technology, is already widespread for cosmetic purposes. This method is currently not used for large-scale medicinal approval, but instead to test if certain people are at risk for certain diseases. 

Computer Modeling 

Of all the alternatives, scientists are most excited about computer modeling techniques. Advanced computer modeling, sometimes called in silica testing, can create complex models of human body systems, even accounting for irregularities like prior diseases, as well as a vast array of genetic and demographic information. 

And they work better than animal models. A 2018 study found an accuracy rate of between 89 percent and 96 percent, while a 2017 study estimated the accuracy rate of one method of analysis at 96 percent: in both studies the computer models beat the animal testing experiments. 

Research Using Human Volunteers

Using human volunteers seems a bit dystopian, but science has progressed a long way since the unethical days of the 20th century. For starters, in some recent drug testing human volunteers only receive a microdose of the drug and are monitored in the presence of medical professionals to ensure safety. This microdosing method is promising, but still needs more research. Other forms of human volunteer research include the safe use of fMRI imaging, which has been shown to be very effective. 

Of course, ethics regarding human volunteers are critical. Scientists and researchers must take great caution not to compel participants into doing something unsafe and must mitigate risks as much as possible. Using human volunteers is also best done after one other method, like computer modeling, has been completed to mitigate risk. 

Animal Testing Facts and Statistics

  • The majority of animals used in animal testing are exempt from the Animal Welfare Act because they are rats or mice.
  • Rats have great memories and demonstrate empathy for other animals.
  • Every year, the NIH spends nearly $20 billion on animal testing-based research.
  • A majority of Americans disapprove of the continued use of animal testing.

What You Can Do

Consumers who want to avoid products tested on animals can look for a “vegan” or “cruelty-free” label when purchasing cosmetic products. They can also voice their support for policies to improve animal welfare in the medical industry like the FDA Modernization Act 2.0, which passed the U.S. Senate earlier this year.

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