Animal experiments and their drawbacks

When exploring the field of animal experiments, one will encounter various websites favoring research on animals. Of course, advocates of animal experiments are typically themselves part of the system and thus defend their own interests. Opponents of animal experiments, however, fight for the interests of animals, which actually means they work themselves out of their job.

While advocates of animal experiments repeatedly emphasize medical progress cannot happen without experimenting on animals, researchers who critically question such experiments repeatedly provide new facts that demonstrate animal experiments pose an incalculable risk, particularly for us humans.

In the following article you will find a selection of arguments that - based on facts - speak against animal experiments. Both ethical aspects as well as scientific arguments will play a role.

1. Results of animal experiments cannot be translated to humans 

For example, age, sex, and lifestyle, among other factors, play a significant role in how the human body responds to drugs. Furthermore, humans and animals differ from each other just as individual animal species do, regarding physique, organ function, metabolism, and diet. These differences suggest results from animal experiments cannot be translated from one animal species to another, and consequently not from animals to humans either.

For example, mice and rats show a match of only 50 percent regarding the carcinogenic effect of substances (1). In another study it was demonstrated the human immune system and that of mice responded very differently to blunt trauma, burns, or sepsis. One million times more bacteria were needed in mice than humans to trigger a lethal septic shock. The human body responded in a much stronger and longer way to inflammation, whereas the response of the mouse’s immune system decreased after only a few days (2). A mouse simply is not a rat, and a human is not a mouse.

Research on Alzheimer’s disease has been using various animal models - as they are called - for decades to study the disease and develop treatment options. While experiments often appear to be successful in mice, not a single drug capable of healing the disease in humans or halting its progress has come out of them (3). One analysis has shown that of over 400 clinical studies on medication given to human patients with Alzheimer’s disease, only 0.4 percent led to an improvement of the clinical symptoms. One reason certainly is the artificial triggering of such unnatural symptoms in animals, which has nothing in common with how the disease progresses in humans.

Research on human mini-brains at Ruhr University Bochum has revealed a mechanism that probably explains how the nerve cells in patients with Alzheimer’s disease die. This finding, which is relevant to humans, is based on research free of animal experiments. Even many more animal experiments would not have been able to conclude such an important finding.

2. Animal experiments give us a false sense of security

The scientific facts are clear: Over 90 percent of all drugs proven effective in animal experiments fail when being tested on humans for the first time (clinical phase 1-3), especially because they either show no effect at all or trigger strong side effects that can even lead to death (6, 7, 8).

Medical scandals have dramatically shown again and again tests on animals do not automatically mean being safe for humans. One example is TGN1412, a potential remedy for multiple sclerosis, which was tested on humans in the clinical phase 1 in 2006 for the first time and led to multiple-organ failure in six human subjects (9). Another example is the therapeutic drug Bia 10-2472 for chronic pain. After being administered to humans in 2016, five subjects experienced severe neurological damage, and one person died (10).

Even after releasing drugs to the market, severe damage not detected in animal experiments can often occur in humans. Of the about 10 percent of the drugs that make it to the market, about one third will be removed or labeled with a warning (11). Examples are the rheumatism drug Vioxx; the heart drug Trasylol; the blood lipid-lowering Lipobay or Zinbryta, a remedy for multiple sclerosis that needed to be taken off the market due to most severe and often lethal side effects.

According to a study of the Hannover Medical School, there are approximately 58,000 fatalities caused by the incorrect intake or undesirable side effects of drugs (12). This number only includes patients dying in the hospitals’ internal medicine departments. Not considered are patients in other departments, outpatients, people dying at home, or patients with chronic long-term consequences caused by the side effects of drugs.

3. Animal experiments block medical progress

In the previous section we discussed many substances working and being effective in animals, yet having the opposite effect in humans, and there has hardly been any drug that was successfully tested in animal experiments and had the desired effect in humans.

It has been known for a long time animal experiments are not suited to develop useful and effective treatment options for humans. Numerous examples from the past prove on the one hand, how misleading animal-based research is, and on the other hand, how future-oriented animal-free research is.

Penicillin, aspirin, and paracetamol, for example, were discovered without animal experiments about 100 years ago and have become indispensable in modern medicine. Back then, today’s requirement to test all potential drugs on a number of animals to ensure their effectiveness and safety did not exist.

These examples demonstrate how useless animal experiments are, because if those drugs had been tested on animals, they would have failed today’s testing requirements and thus would have never been released to the market and we humans would have been deprived of them. For example, while aspirin has no negative impact on unborn human babies, it leads to deformation in unborn mice, rats, and monkeys (13). Penicillin is lethal for guinea pigs and rabbits, yet is life-saving for humans (14). Paracetamol causes cancer in rodents and is poisonous for cats.

Who knows how many perhaps effective drugs are prematurely removed and will never make it to the market due to causing damage in animals. If we do not fully distance ourselves from animal experiments, medical progress will continue to be blocked. Precious medical findings do not exist because, but in spite of animal experiments! Especially findings gained from human population studies and human-based research methods play a leading role.

4. Animals are no suitable “models” for humans

Animals are used as so-called “models” to conduct research on human diseases. The term “animal model” suggests animals are representations of humans to research human diseases and find possible cures. For almost every question or disease there is a range of different “animal models,” e.g., for cancer, diabetes, Alzheimer’s disease, heart diseases, and even depression.

These “animal models,” however, are by no means representative of us humans. The fundamental problem is human diseases are reduced to their symptoms in the animal and induced artificially, which has nothing to do with the actual development of the disease in humans.

Cancer and Alzheimer’s disease are triggered in mice through gene manipulation; a stroke is imitated by clogging a brain artery in rats or mice; and in depression research, rats are forced to swim in an unescapable water container until exhaustion.

These “animal models” are unnaturally constructed far away from reality and are in no way suited to explore the complex connections in the development of human diseases as they completely ignore critical factors, such as age, sex, genetics, diet, stress, and environmental aspects. It is therefore not surprising animal experiments do not advance medical progress but rather impede it.

Even “improved” animal experiments, as often propagated by experimenters, cannot change the fact that results of animal experiments always place an incalculable risk regarding the translation to humans.

5. Animal experiments as a lottery game - results are not reproducible

Animal experiments are conducted under standardized and sterile conditions - as they are called - so the results are as reproducible as possible, i.e., they can be repeated. Therefore, animals of the same age, sex, and weight are used. The decisions on what to feed and how to house animals also follow constant laboratory conditions.

Apart from the fact we humans, who are supposed to be represented by the animals in the lab, do not at all live under such artificial standards in real life, even one and the same animal experiment conducted in those unrealistic lab conditions frequently produce varying results. This is partially due to the fact that each animal is an individual and the factors influencing the development of diseases (lifestyle, stress, age, sex, genes, among others) are ignored in those artificial lab conditions.

How the animals are handled can additionally distort the results, e.g., through the level of stress they experience. Typically rats and mice, inter alia, are kept in a sterile environment in small plastic boxes with some bedding and the boxes being stacked on each other. It was shown animals are willing to work for the opportunity to experience an interesting environment, build nests, or socialize with their conspecifics. Rats in a sterile environment have smaller brains than animals in a diverse environment, and rats kept secluded from others try more frequently to escape their cages than rats living in groups. The behavioral researcher Dr. Jonathan Balcombe of the Physicians Committee for Responsible Medicine (PCRM) in Washington drew these conclusions after evaluating 200 publications on the housing conditions of rodents (15).

Animal experiments regarding the translation to humans are a lottery game that brings incalculable risks for humans and means a painful, useless death for the animals. For we can only know after testing the substance on humans if an animal - and if so, which animal species - responds to that substance in the same way as the human body.

Every other scientific method combining as many factors of uncertainty and being as unreliable and unpredictable as animal experiments would be immediately sorted out.

6. Wasting tax money

Apart from the field of animal experiments being scientifically unjustifiable, animal experiments are a huge waste of money. In Germany alone, this field of research is subsidized with billions of euros annually, and that money mainly comes from tax revenue. Of the subsidies, less than one percent goes to animal-free research, while the rest supports animal experiments.

7. Unethical toward humans

As long as medical research keeps using animal experiments as its gold standard, effective drugs and treatment options will continue to be kept from us, because they will be removed due to misleading animal experiments. At the same time, it can be assumed humans will continue to be victims of the side effects of drugs that appear to be safe in animal experiments but do not hold up in reality.

Animal experiments therefore are not only unethical toward animals but also toward patients who are exposed to risks or kept from treatment options due to misleading results in animal experiments.

 

8. Animal-free research methods are superior to animal experiments

In the previous section we have seen animal experiments are a fatal error from both an ethical and a scientific point of view.

In our modern age there are a variety of animal-free research methods, such as multi-organ chips, epidemiological research, or computer simulations that provide fantastic and - with regard to the translation to the human body - reliable results.

At the University Hospital Charité in Berlin, for example, researchers have found a drug for Leigh syndrome, which used to be an incurable disease of the central nervous system. They did not find the drug through animal experiments but through modern, patient-specific research. A 15-year-old patient who was already paralyzed, unconscious, and had to be artificially respirated was treated with this new method. Out of the patient’s cells, the researchers first obtained induced pluripotent stem cells that were then converted into neuronal cells. That way, new cells of the central nervous system developed which were used to test potentially effective drugs. One drug already approved for another disease turned out to be successful.

In the researchers’ statement it says, “Spectacular about it was not only the successful treatment. All the animal experiments had failed to find a treatment option for Leigh syndrome (16).”

Our NAT Database on non-animal technologies lists thousands of such modern animal-free methods.

9. Why do animal experiments still exist?

Even though arguments against animal experiments are clear and scientific facts suggest the elimination of animal experiments rather today than tomorrow, there are numerous reasons for why this field of research continues.

Tradition

Animal experiments look back on a long tradition. They have been established as a “method of choice” in science since the middle of the 19th century. Only what can be demonstrated in animal experiments counts as scientifically proven. This dogma not only exists in the heads of many researchers but also in biomedical science programs and in a variety of laws - despite knowing better.

Career opportunities

Following the motto “publish or perish,” scientists are under enormous pressure to publish their findings in renowned scientific journals of high impact. Only through such publications may they increase their reputation. And since many scientific journals of high impact mainly publish animal experiments, it is the easiest way to have a career. The more a researcher publishes, the more subsidies they receive and can then use for more animal experiments in order to publish even more. It is a self-sustaining system.

Financial support

Due to the pronounced unequal distribution of funding in favor of animal experiments, career and earning opportunities are naturally significantly better in research using animal experiments. Those who devote themselves to modern animal-free research instead receive little financial attention in spite of all the medical-scientific benefits this kind of research entails.

Conclusion

The discussed facts on animal experiments and their drawbacks make it clear there are no logical or even scientific reasons to continue experiments on animals. Yet this completely fatal system without any reliable scientific foundation has anchored itself in our society. To establish exhaustive modern and ethical research, it is crucial to turn away from animal experiments. Sophisticated and diverse animal-free research methods that focus on humans make it possible to conduct tailored research that - in contrast to animal experiments - enables medical progress and spares animals a meaningless death.

06/05/2021
updated 04/04/2025
Dipl.-Biol. Silke Strittmatter

The failure of animal experiments - an animated educational film“

 

References

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2. Seok J et al. Genomic responses in mouse models poorly mimic human inflammatory diseases. PNAS 2013; 110(9):3507–3512
3. Langley GR. Considering a new paradigm for Alzheimer's disease research. Drug Discovery Today 2014; 19(8):1114-1124
4. Cummings JL et al. Alzheimer’s disease drug-development pipeline: few candidates, frequent failures. Alzheimer’s Research & Therapy 2014; 6(4): 37
5. Ruhr-Uni-Bochum. Alzheimer im Mini-Gehirn, 30/04/2019
6. Clinical development success rates 2006-2015. BIO, Biomedtracker, Amplion 2016
7. Clinical development success rates 2011-2020. BIO, Informa, QLS Advisor 2021
8. Why are clinical development success rates falling. Biomedtracker Citeline 29/04/2024
9. Wikipedia: TGN1412 [accessed 17/03/2021]
10. Wikipedia: BIA 10-2474 [accessed 17/03/2021]
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12. Schnurrer JU et al. Zur Häufigkeit und Vermeidbarkeit von tödlichen unerwünschten Arzneimittelwirkungen. Der Internist 2003, 44:889-895
13. Hartung T. Per aspirin ad astra. ATLA 2009; 37:45-47
14. Doctors Against Animal Experiments: 1929 – Penicillin 
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16. Gesundheitsstadt Berlin GmbH: Stammzellen statt Tierversuche: Charité-Forscher finden erstmals Medikament gegen das unheilbare Leigh Syndrom, 02/03/2021