To the extent that I understand, it’s not that they are using toxic chemicals, but rather that they want to make sure that the amounts that they are using and the combination of all of the chemicals isn’t harmful.
This is because they don’t know how the mixture will turn out until they actually try it out, and getting humans to do it would imply lots of liabilities they can avoid by using animals.
I’m definitely not an expert on this topic but to give an explanation in case no one else does here is my best explanation, as someone who very briefly covered this in university.
When you make a new product for consumption or to be applied to skin like makeup you need to make sure that it isn’t going to kill the person using it or cause any negative reactions in the body. Can’t go around selling people pain killers that are going to damage their livers.
You can do computer models to get a rough idea of what it might do to a living thing but having a simulation say that a substance is fine for consumption isn’t enough because chemistry is complex and models are supposed to be simplified versions of the real thing. If the computer model doesn’t show anything bad you might then test on a tissue sample which will give you a better idea of if it’s safe to use on humans. Testing on a tissue sample is better because it’s an actual living thing and if the substance you’re testing kills the cells then that’s obviously bad and you shouldn’t be eating it, but again chemistry/ biology is complex and testing on tissue samples isn’t going to give you the whole picture.
After tissue samples the next thing to test on is animals, it’s generally considered unethical to feed people random crap to see if it harms them, but you can’t just not make new medicine so I guess the next best thing is to test on a living being that isn’t human. Primates are best because they have a very similar biology to humans. If something harms a monkey it’s probably going to harm a human. Macaques are used a lot, I don’t know why we chose those over other primates, they’re kinda expensive though so other times we test on mice or rats because surprisingly they also have a similar biology to us (not as similar as monkeys) and they’re a lot cheaper.
Once you’ve tested on animals you can be fairly certain that your new drug (or shampoo or whatever) isn’t going to kill people if they use it, but however similar an animal is to us it’s not good enough. Differences do exist like how we can eat chocolate just fine but you shouldn’t feed it to your dog. So the final step is to test the new product on a small group of humans, always volunteers and (usually) paid since they’re taking a medical risk. If you get past animal testing the human tests are unlikely to show anything new about harmful effects but in rare cases they do and people end up dying, so it’s a good job we decided to test on a select group rather than just throwing that stuff in to the market.
Biology students (at least in the UK) are actually forced to participate in one human drug trial to the best of my knowledge. I guess the logic is if you’re going to eventually test substances on other people you better be willing to be tested on yourself so you’re willing to go to extreme lengths to make sure your own substances are safe before moving on to human trials.
A lot of people (including me) think that animal testing is immoral because monkeys or mice can’t consent to being tested on but the alternative is to kill a lot of people when testing new stuff so it’s a necessary evil, if you see animal lives as being less valuable than human lives.
Edit: I just realized you specified makeup companies but I focused on drug companies (it’s 6 AM and I haven’t slept, sorry). The rationale is the same though. If you’re selling eyeliner to people you better be damn sure it isn’t going to blind them.
Edit 2: I think it’s interesting to consider what a chemical really is too. I’m not a chemist so I can’t give a good explanation but most people hear the word “chemical” and assume that it’s dangerous but most things in the natural world are chemicals. The danger comes from unnatural chemicals like plastics. Consider reading this to learn more: https://en.m.wikipedia.org/wiki/Dihydrogen_monoxide_parody
From a pharmacist’s prospective though cosmetics is also applicable:
We perform animal testing to establish safety of a product, for drugs we use some in-vitro testing first (experiments that do not use animals) first such as skin grafts, eye models and check for toxicity if any. Then we move into animal models to verify the toxicologic data we got from in-vitro study.
We can’t simply not test for toxicity since your product would not be approved by your local food and drug administration, FDA, though usually you hear is bad things about them in the new, is very strict when it comes to new products.
However, unless your makeup contains new ingredients such as new colorants or dyes, your formulation would most likely use already established ingredients that may be included in the GRAS list – “Generally Regarded as Safe”, the ingredients in the list need not prove their safety since from the name itself, regarded as safe. It would also be more economical for the makeup company to not perform safety studies so makeup companies would now start to stray away from new ingredients unless they really need to.
In terms of animal models the most common test model for skin toxicity is Rabbits. You may search “Draize Eye and Skin Irritation Test” (Though it may be very graphic for some)
References:[https://www.fda.gov/cosmetics/cosmetics-laws-regulations/fda-authority-over-cosmetics-how-cosmetics-are-not-fda-approved-are-fda-regulated](https://www.fda.gov/cosmetics/cosmetics-laws-regulations/fda-authority-over-cosmetics-how-cosmetics-are-not-fda-approved-are-fda-regulated)
GRAS Database – [https://www.cfsanappsexternal.fda.gov/scripts/fdcc/?set=SCOGS](https://www.cfsanappsexternal.fda.gov/scripts/fdcc/?set=SCOGS)
A friend worked for a cosmetics company. And basically you can’t just release whatever you want to the public. The FDA would shut you down so fast.
So you have to go through testing. One example my friend told me about was a lotion. They tested it on rats and none of them had bad reactions so they moved on to human trials, where 1.5% of the population got rashes from the lotion, it worked as intended for the other 98.5% of people. But because of that, they couldn’t sell that product.
Anyway, they test on animals because if any of those rats reacted poorly, they never would have gone to human trials.
Animal trials are much cheaper. You can buy 50 rats for testing for the same cost as 1 hour of one human’s time.
So testing on animals potentially avoids the expensive part of trials, should a new product not be viable.
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