350,000
Chemicals in commercial use worldwide
IN SHORT
Most brands check an ingredient list. We test the final formula.
An endocrine disruptor is a chemical that interferes with the body's hormones. No law requires cosmetics to be tested for it, so brands usually just compare their ingredients against a short published list. Nothing is sent to a laboratory.
Those lists are small. Around 350,000 chemicals are in use, and fewer than 800 are even suspected. Chemicals also behave differently together than alone.
So we do not rely on a list. We test each finished formula on human hormone receptors before it launches.
We are the first brand in the world to do this, and every formula is tested free of estrogenic and androgenic endocrine disruption.
What is an endocrine disruptor?
An endocrine disruptor is a chemical from outside the body that interferes with some part of that process, and causes harm as a result. That is the World Health Organization's definition, and European law is built on the same wording. The Endocrine Society uses a wider one, which is any chemical that interferes with how hormones work.
That difference matters. Under the first definition, a chemical is not called an endocrine disruptor until somebody has proven that it causes harm. Somebody has to go looking first.
Hormones are the messages our bodies run on. They are made in one place, carried through the blood, read by cells somewhere else, then cleared away. That quiet system decides a great deal about how we grow, how we heal and how we age.
Why they reach further than most of us think
For a long time we were told that our health was written in our genes. What research keeps showing is that the same genes can be read in different ways, depending on everything around us. That is epigenetics, and it is where our own work began.
Endocrine disrupting chemicals have been recognized as epigenetic factors. They can change how genes are read without changing the genes themselves.
So although we started testing our products for our concern of hormone disruption on women, this topic is no longer just a women's question. Every body runs on the same hormonal signaling, so the concern reaches men as much as women, and it reaches young people, whose bodies are the most sensitive of all.
A message works at a whisper
Classical toxicology has a rule. The dose makes the poison. A substance is harmless until there is enough of it to do harm.
Hormones are the exception. They act as messages, and a message works at a whisper. Some act at concentrations of parts per trillion. In other words, one drop in 20 Olympic pools. That is the dose needed to have an impact.
So a chemical that mimics a hormone can send a signal while remaining far too dilute to register as a toxin. Small does not mean silent.
This is why we do not clear a formula on dose alone. We measure whether the finished formula sends a hormonal signal at all.
What the industry does
If you assume that ingredient suppliers test for endocrine disruption, and that brands then choose from whatever has been cleared, you are wrong.
European chemicals law asks for no endocrine testing. Cosmetics law asks for none either. So when a brand says it avoids endocrine disruptors, what it usually means is that somebody compared the ingredient list against a published list of substances to avoid. No sample is sent to a laboratory. Nothing is measured or tested.
The problem is that the published lists are very short. Around 350,000 chemicals are in commercial use worldwide. The World Health Organization counts close to 800 that are known or suspected to interfere with hormones. The European Community set a list of 28 substances as priority in 2009, of which 1 has been banned and 8 substances limited in dose (this is as of 2016). For cosmetics, the European Commission drew up a review list of 28 substances in 2019, and has acted on six of them so far. It can take up to a decade for a single ingredient to make the list, studied, analysed, and debated one at a time.
So a list of substances to avoid protects you from the handful of chemicals that somebody has already named. Every other molecule in the formula goes unquestioned when there are so many suspected.
800
Known or suspected to interfere with hormones
28
Suspected substances set as priority in 2009 by the EU
1
Substance banned in the EU as of 2026
The ones that have been named.
These are among the few that authorities have already identified
The point is not the list. It is how short it is, next to the hundreds of thousands of chemicals in use.
In everyday products and packaging
Bisphenol A, known, in polycarbonate plastics, the linings of food cans, and thermal receipts. Restricted in several uses under EU law.
Certain phthalates, such as DEHP, known or suspected, in flexible plastics and food packaging. On the EU priority list.
PFAS, an emerging concern, in grease and water resistant coatings.
In some personal care
Certain parabens, such as propylparaben and butylparaben, suspected, used as preservatives. Some restricted by the EU scientific committee.
Some phthalates, such as diethyl phthalate, suspected, used in fragrance.
Certain UV filters, such as benzophenone-3, suspected, used in some sunscreens and under EU review.
Triclosan, suspected, an antibacterial agent restricted in the EU.
In agriculture and the wider environment
Certain pesticides, such as atrazine and vinclozolin, identified in research by the Endocrine Society.
Some flame retardants and industrial chemicals, such as nonylphenol, suspected.
Every entry above took years of study to name, one at a time. Now look again at the numbers. Around 350,000 chemicals are in use, close to 800 are known or suspected, and only a handful have been acted on. A list protects you from the named. It cannot protect you from the unquestioned.
That is why we do not check a formula against a list. We test the finished formula itself.
What we do
We test the finished formula.
We begin from the opposite assumption to the rest of the industry. Rather than treating a molecule as safe because nobody has banned it yet, we treat every formula as an open question until the measurement comes back.
Chemicals also behave differently in company than they do alone. Scientists call this the cocktail effect. In one well known experiment, eight weak estrogenic chemicals were each used below the level at which they do anything measurable on their own. Together they produced a clear estrogenic effect. An ingredient list would have failed at detecting.
Skin Diligent tests the final formula on living cells that carry the human estrogen receptor and the human androgen receptor, measured against the hormones themselves. The method is part of OECD's ISO 19040-1. The model behind the test is deliberately unforgiving, because it assumes that every drop of the product passes through the skin into 5 liters of blood, and that the body breaks none of the product down.
Every formula is tested this way before we launch it, and every one is tested free of estrogenic and androgenic endocrine disruption.
FAQ
What are endocrine disruptors?
Chemicals that interfere with how hormones work, and cause harm as a result. Some copy a hormone. Some block one. Others change how much of a hormone the body makes, moves or clears away.
Is clean beauty the same as hormone safe?
No. Clean is a promise about what has been left out of a formula. Hormone safety is a measurement of what the formula actually does. Plant derived ingredients can be hormonally active too, so natural tells you very little either way.
Is natural and organic the same as hormone safe?
No. The EU list of endocrine disruptors include natural ingredients. And our own tests in the lab have shown the same, which makes us reformulate and test again. Organic is a method of plant growth. The plant molecules are the same whether they are organic or not.
Can skincare be certified free of endocrine disruptors?
No. There is no certification anywhere in the world that certifies a cosmetic free of hormonal activity on the basis of testing, because there is nothing yet to certify against. We publish the testing instead.
Which skincare brands test for endocrine disruption?
There is no public register and no certification exists. Most brands answer the question by comparing their ingredient list against a published list of substances to avoid, which involves no laboratory and no measurement. Skin Diligent measures every finished formula for estrogenic and androgenic activity, and was the first brand in the world to do so.
Do endocrine disruptors affect women and men?
Yes. Every body runs on the same hormonal signaling, whatever its age or sex. Children are the most sensitive of all, which is why the concern is greatest during pregnancy, infancy and adolescence.
Does the law require endocrine testing of cosmetics?
No. No regulator in the United States, the United Kingdom or the European Union (or anywhere in the world) requires an endocrine test of a cosmetic ingredient or a finished cosmetic product. We test because we believe the question should be answered.
Tested, not assumed.
Sources: International Programme on Chemical Safety, Global Assessment of the State-of-the-Science of Endocrine Disruptors, WHO, 2002. Gore AC et al., EDC-2: The Endocrine Society's Second Scientific Statement on Endocrine-Disrupting Chemicals, *Endocrine Reviews* 2015;36(6):E1-E150. La Merrill MA et al., Consensus on the key characteristics of endocrine-disrupting chemicals, *Nature Reviews Endocrinology* 2020;16(1):45-57. Silva E, Rajapakse N, Kortenkamp A, Something from "Nothing", *Environmental Science & Technology* 2002;36(8):1751-1756. Wang Z et al., Toward a Global Understanding of Chemical Pollution, *Environmental Science & Technology* 2020;54(5):2575-2584. Dolinoy DC, Huang D, Jirtle RL, *PNAS* 2007;104(32):13056-13061. Manikkam M et al., *PLoS ONE* 2013;8(1):e55387. European Commission Staff Working Document SWD(2020) 251, Fitness Check on endocrine disruptors. Vandenberg LN, Colborn T, Hayes TB, et al. Hormones and endocrine-disrupting chemicals: low-dose effects and nonmonotonic dose responses. Endocrine Reviews. 2012;33(3):378-455. World Health Organization, Global Assessment of the State-of-the-Science of Endocrine Disruptors, 2012. EU priority and cosmetics review lists, and SCCS opinions, for the specific classifications above.