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Toxic chemicals: what does it even mean?

Anyone who had ever tried to research cosmetic ingredients have most likely seen some of them highlighted by various websites as “toxic”. Unfortunately, most of these claims are either not based on science, or based on an outdated science. Fear is a major driver to click the link and is good for website owners, but most of the time it doesn’t help the consumers and just causes unnecessary anxiety.

So what does “toxic” mean? Per Wikipedia, toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. It can have an effect on a cell (cytotoxicity) in the context of the skin care products or an organ such as the liver (hepatotoxicity) if we are talking about the products that are able to penetrate the skin and reach the bloodstream.

Essential oils for instance are cytotoxic, as well as some plant extracts. However, most people consider them “natural” or read “organic” label and presume it is safe. Does it mean we shouldn’t use essential oils and extracts in cosmetic products at all? Well, it goes back to the benefit/safety analysis and the dose that is planned to be used. Indeed, in most cosmetic products the amount of essential oils and extracts is present at a such low levels to avoid cytotoxic effects including irritation, that benefits of their use are barely noticeable. And certainly we wouldn’t use either of these intravenously.

What is important to remember is that our skin is an amazing tool: not only it has several physical protective layers, it also produces various enzymes to help “process” the substances that happen to land on its surface. For example, lipase helps to break down oils and the enzyme with the cool name CYP26AI is responsible for the metabolism of retinoic acid in skin cells.

Our liver has even more enzymes. Think of a toxic substance called ethanol: if a large dose of it is consumed, it would kill a human. If a high concentration is applied to the skin for a prolonged time it would cause an irritation and a burning sensation. However, a small dose can be safely processed by our liver and the extra small is even produced by our own body. To be more precise, our gut biota that can convert very small amounts of carbohydrates into alcohol.

So how to figure out what is dangerous to have in cosmetic products and what is actually fine? This is a tricky question that usually requires a panel of scientists to look at all available research and determine the answer based on the following factors:

  • What is the total typical exposure to this ingredients. For example, if it is present not only in cosmetic products, but also in food it increases the exposure tremendously. At the same time the amount of this ingredient in these products (if present at a very low concentrations) might not add up too much.
  • What is the metabolism of this chemical: in what way and how much our body can safely process? Are there any circumstances when the metabolism is impaired and the processing doesn’t work as well – in particular in small children or when skin is severely burned.
  • Does it penetrate the skin and reach the bloodstream? If that is the case, are there studies showing what amounts are safely processed and what is the unsafe threshold. Similarly, what would be the factors impacting one’s ability to safely metabolize this ingredient?
  • What would be a safety threshold to take into the account: if any of the factors above are calculated incorrectly, there still should be a room for mistake when recommending a safe does of the ingredient. Sometimes this threshold can be thousands times higher simply to stay on the safe side.

The reason why we need a panel of scientists is that this analysis involves several different fields of science: toxicologists, chemists, dermatologists and cell biologists. There are tons of studies that just take a bunch of cells, throw them into an ingredient and describe some damaging effect. Although it might be a necessary step in the scientific research, it doesn’t readily translate into the level of safety of the ingredient for humans, as it doesn’t account for the metabolic processes we normally have.

Similarly, many studies done on animals imply either high levels of consumption of ingredients in question or a 100% concentration when applied onto the skin. Although it helps to understand the doses that are definitely lethal or carcinogenic, again, they don’t tell us much about toxicity of an ingredient if used at a lower concentration.

In the US this panel of scientists is known as Cosmetic Ingredient Review  for cosmetic ingredients while Food and Drug Administration along with the Centers for Disease Control and Prevention assess the safety of food and drug ingredients. Since certain cosmetic ingredients are also used in food or drugs, sometimes a different agency would take the responsibility to perform the analysis and provide the recommendation.

In the EU the Scientific Committee on Consumer Safety is the primary scientific body providing opinions on ingredients safety and recommended levels in cosmetic products. If ever in doubt, don’t click the random sites for contradicting opinion, google the ingredient name and the name of one of the organizations above to know the stance on a particular ingredient by the most qualified scientists. For example: “FDA phtalates”.

Sometimes opinions between the organizations differ, mostly it is related to the safety threshold each organization decides to apply, rather than actual disagreement about the ingredient’s toxicity. Sometimes the opinions on ingredients change, as more data becomes available and it can be changed both ways: to become more restrictive temporarily, until the issue is cleared with more data; or to allow higher usage once more research becomes available and provides enough confidence to the review panel.

And the most important part: those ingredients that are really toxic are already banned from cosmetic products. So when you see an article promising to tell you the toxic ingredients to avoid, take it with a grain of salt, but keep in mind that salt is cytotoxic too!

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