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Animal experiments can be criticised in a number of respects:


Because animals do not get many of the diseases humans do, such as heart disease, many types of cancer, HIV, Parkinson’s disease, or schizophrenia, these have to be artificially induced. To mimic the human disease researchers inject animal with poisons, destroy parts of their brains, put them in stressful situations, implant human cells and tissue into their bodies or genetically engineer them to have human genes. The resulting ‘animal models’ may only superficially have the same disease as humans, increasing the risk that the wrong assumptions about cause and treatments are made. Add to this the inescapable differences in physiology between human and other animals, and the chances that these ‘animal models’ predict accurately what might happen to a human patient are very small.

For example, Fran Visco, founder of the National Breast Cancer Coalition said, “Animals don’t reflect the reality of cancer in humans. We cure cancer in animals all the time, but not in people”. (We fought cancer…And cancer won. Newsweek, Sep 5, 2008). 

Not predictive

Due to the high variability of the results between sexes and strains of animal and laboratories, the high doses used, high stress levels and poor methodology, in addition to species differences, it is not surprising that animal tests do not appear to accurately predict human effects. Indeed, if you evaluate these experiments it is fair to say that overall animal tests are predictive of human reactions less than half the time. You might as well pay someone to sit in a room and toss a coin. The few studies that have been done to look at how predictive animal tests are of human effects have been damning (see Animal Testing on Trial).

Currently, nine out of ten experimental drugs fail in clinical studies because we cannot accurately predict how they will behave in people based on laboratory and animal studies.” (Mike Leavitt, Health and Human Services Secretary, Food and Drug Administration Press Release Jan 12th 2006)


Because animal experiments do not provide definitive data about human responses, scientists, officials and companies can and do dispute their relevance when it suits them to do so. For example agricultural biotechnology giant Monsanto has recently disputed a rat experiment that suggested a link between their genetically modified (GM) maize and weed killer and cancer, claiming; “the study does not meet minimum acceptable standards for this type of scientific research” (The Guardian 28/09/12).

Sadly, because of inherent doubts about the validity of animal tests, experiments are often repeated by other researchers or companies in order to determine ‘once and for all’ if their ideas are correct. Animal tests exacerbated years of dialogue and debate (and no action) on substances such as asbestos, smoking, saccharin and bisphenol A. Fears about nanoparticles, GM food, and endocrine disrupters are currently being used to justify animal tests but sadly it is unlikely that until adverse effects are seen in humans real governmental action will be taken.


Due to the lack of predictability of animal tests and sheer number of tests that are conducted, the entire process is extremely ineffective, wasteful and expensive. Despite considerable effort over many decades creating ‘animal models’ of conditions like stroke, Alzheimer's, HIV, Type 1 diabetes and multiple sclerosis, we do not yet have reliable and effective treatments. And, despite the scientific community using over 115 million animals globally every year, the main drug regulator, the FDA, approved only 35 new medicines in 2012. (Food and Drug Administration USA. FY 2012 Innovative Drug Approvals - Report. December 2012). Reliance on such an inefficient system would not be tolerated in other sectors of professional business.

Out of date

Drug development today is concentrated on highly targeted biological, cell and gene-based therapies. The differences between species at these levels make it even more difficult and dangerous to use animals to predict human outcomes. For example, in 2006 volunteers testing a novel monoclonal antibody treatment (TGN1412) at Northwick Park Hospital suffered a severe allergic reaction and nearly died. Tests on monkeys at 500 times the dose given to the volunteers totally failed to predict the severe side effects. Laboratory tests not using animals that were performed immediately after the event could have actually predicted the effects. (Duff, G.W. (2006) Expert Group on Phase One Clinical Trials: Independent report to the Secretary of State for Health. 7 December 2006. The Stationery Office; London UK. P.65).

We need to start using 21st century tests for 21st century medicines.

These types of drugs [biologicals] make up more than 50% of new drug applications. We can't use toxicology that is 60 years old.” - Professor Thomas Hartung, former head of the European Centre for the Validation of Alternative Methods, quoted in Nature 2006,440, 856 (following the trial disaster).

Expensive and slow

Individual animal tests can take many years and cost thousands of pounds. For example the rodent carcinogenicity test to predict if a chemical will cause cancer is not only extremely unreliable but takes two years to complete and one million Euros to perform. (Which drugs cause cancer? British Medical Journal 2005, 19: 97-104).

Animal experiments have been used for hundreds of years and it’s time to move on. Whenever and wherever resources are ploughed into developing non-animal techniques, quicker, more reliable and cheaper tests result. We need more money, time and resources devoted to this. For more information see Alternatives to Animals