A while back there was a lot of discussion going on about animal rights activists threatening not only researchers that conducted animal testing, but even their children. A lot of the discussion has been related to animal testing for medical science, where there’s a strong case to be made for it. Animal testing for cosmetics is perhaps another issue though, since strictly speaking cosmetics aren’t as important as medical advances (at least not to me). It is possible to develop new cosmetics without animal testing though?
Cosmetics (and other products applied to skin) generally need to be tested to determine whether they are corrosive and whether they cause irritation. Traditionally this has been done using what is called a Draize test, which basically involves shaving a small area of skin on an animal (usually an albino rabbit) and applying a small amount of the substance to the skin for a specified amount of time. The animal is then observed for several days afterward for evidence of effects such as redness of the skin (erythema) or fluid accumulation (oedema).
While there are a lot of variants on this test, depending on the regulatory agency involved and the laboratory performing the test, these days it is often initially performed using a single animal, with additional animals tested later if the first one is unaffected.
While the number of animals involved is minimal, if the substance is corrosive or an irritant it can cause pain and discomfort to one or more animals, and therefore there are some ethical considerations.
More recently, several in vitro tests have been developed, primarily using artificial skin or skin models. A few examples include:
- Transcutaneous Electrical Resistance (TER), which measures electrical resistance and dye penetration across a piece of rat or human skin to evaluate the corrosivity of a substance (a rat is normally killed to get the skin, so there are again some ethical issues, though enough skin is obtained from a single rat to test several substances).
- Human Skin Model test, in which an artificial skin is constructed from epithelial cells and a stratum corneum (the outer layer of the skin), and effects on cell viability are used to determine whether the substance is corrosive.
- The Irritection Assay System, in which the substance is applied to a membrane with keratin and collagen, beneath which is a protein solution. If an irritant penetrates the membrane, turbidity of the protein solution is increased. A similar approach, Corrositex(R) is used for testing corrosivity.
Several of these tests are now accepted by regulatory agencies such as OECD (the Organization for Economic Cooperation and Development) for testing of corrosivity of chemicals, and could be used instead of animal testing. There may still be some requirement for animal testing to confirm negative results, but the likelihood of the substance harming the animal would be low in this case.
At this stage, there are very few in vitro tests for irritation however, and they do not have much regulatory acceptance. Therefore, animal testing is still necessary to determine whether a substance is an irritant. Hopefully the tests for irritation will continue to be developed and progress to the point where they can replace animal testing. Since the in vitro tests are not only more ethical, but also cheaper and faster, there is an incentive for getting these methods to this stage.
In summary, we’re progressing towards the point where, at least for corrosion and irritation testing, animal testing could become obsolete in the near future. At present, however, some animal testing is still necessary for cosmetic products (whether it is appropriate to risk harming an animal simply to develop a new cosmetic product is a purely ethical issue and one I’m not going to tackle here).
OECD (Organization for Economic Cooperation and Development). 2002. OECD Guideline for the Testing of Chemicals: Acute Dermal Irritation/Corrosion. OECD Guideline 404. Adopted April 24, 2002.
US EPA (United States Environmental Protection Agency). 1996. Human Health Effects Test Guidelines OPPTS 870.2500: Acute Dermal Irritation. Prevention, Pesticides and Toxic Substances. EPA712-C-96-196.
OECD (Organization for Economic Cooperation and Development). 2004. OECD Guideline for the Testing of Chemicals: In Vitro Skin Corrosion: Transcutaneous Electrical Resistance Test (TER). OECD Guideline 430. Adopted April 13, 2004.
NICEATM (The National Toxicology Program (NTP) Interagency Center for the Evaluation of Alternative Toxicological Methods). 2001. EpiskinTM, EpiDermTM, and Rat Skin Transcutaneous Electrical Resistance (TER) – In Vitro Test Methods for Assessing the Dermal Corrosivity Potential of Chemicals. National Institute of Environmental Health Sciences (NIEHS), Research Triangle Park.
OECD (Organization for Economic Cooperation and Development). 2004. OECD Guideline for the Testing of Chemicals: In Vitro Skin Corrosion: Human Skin Model. OECD Guideline 431. Adopted April 13, 2004
OECD (Organization for Economic Cooperation and Development). 2006. OECD Guideline for the Testing of Chemicals: In Vitro Membrane Barrier Test for Skin Corrosion. OECD Guideline 435. Adopted July 19, 2006.