Why You Can't Just Read the Label: Tattoo Ink, Trade Secrets and What Testing Found

When an ink manufacturer says an ingredient is a trade secret, I want to know what the safety sheet still has to disclose. I used to think the phrase explained most of the missing information. Reading the rule and the ink surveys changed that.

What people assume it means

The common assumption, and I held it myself for years, is that "trade secret" is a way to keep a dangerous ingredient off the paperwork. If the hazard isn't named, nobody can object to it.

The rule allows some information to be withheld, but it doesn't allow the hazard to disappear with it.

What the rule actually says

US hazard communication law permits withholding, under 29 CFR 1910.1200(i). A manufacturer may withhold the specific chemical identity of a hazardous ingredient, and/or its exact percentage, from Section 3 of a safety data sheet. No prior approval is needed. Companies across the industry use it, and you will see it stated on real sheets.

Withholding comes with conditions.

The trade-secret claim has to be supportable, and the sheet must say that the identity is being withheld. If the concentration is withheld, a prescribed concentration range still has to be supplied.

The chemical's properties and effects must also be disclosed. Guidance allows a name such as 'Component A,' but the health hazards and signs of exposure still belong on the sheet. A claim that fails regulatory scrutiny can be a citable violation.

A health professional can request the withheld identity, and a refusal has to come with evidence supporting the claim.

So an invoked trade secret hides the name, not the danger. A company concealing a sensitiser behind "Component A" is still legally obligated to tell you it's a sensitiser. Hiding the hazard as well isn't a loophole; it's a violation.

Why the provision exists at all

There are real reasons to use it, and as someone who sells custom formulations I understand them from both sides.

The pigment itself is a commodity. Anyone can buy PB15:3 or carbon black. What carries the value in an ink is the dispersion package, the surfactant system, the grind, the particle size distribution and the ratios. That's the part that took years to get right, and a published formulation is a copied formulation.

Protecting how an ink is made is legitimate. Refusing to say which pigment is in it is a different thing.

The gap that actually costs you

The gap I had missed was the classification that comes before any trade-secret claim.

The trade secret route only governs ingredients classified as hazardous. A manufacturer that classifies its product as non-hazardous has no Section 3 disclosure to withhold in the first place, and never has to claim a secret at all. There's nothing to hide behind because there's nothing required.

That classification is self-certified. The manufacturer decides it.

A declared trade secret leaves something visible to question: the statement is on the sheet, and health professionals have a route to request the identity. A non-hazardous classification may leave much less detail to examine. That is why I ask how the classification was reached, as well as what the manufacturer is withholding.

If you've been worried about the sheets that say "trade secret," worry less. Worry about the ones that say the product has no known significant effects across every endpoint and list four generic ingredients.

And when inks are actually tested, the labels are wrong anyway

Researchers have obtained inks and their paperwork, then compared the stated ingredients with analytical results. The disagreement goes beyond a withheld chemical name.

In a 2021 European survey of 73 inks, the open-market products had substantial labeling problems.

Ninety-three percent violated EU labeling requirements, and half declared at least one pigment incorrectly. Only 37.7% of the pigments detected appeared on the labels. Undeclared polyethylene glycol was found in 37.5% of the inks, and 61% contained pigments of concern, particularly among reds.

A 2024 US analysis examined 54 inks in six colors from nine manufacturers.

Only six matched their stated composition completely, and only 29 listed their pigments correctly. Forty-five inks from eight manufacturers had unlisted pigments or additives. Some labels listed glycerol where the analysis didn't detect it.

Both studies found errors running in both directions: ingredients present that weren't declared, and ingredients declared that weren't present.

Why polyethylene glycol keeps showing up

That PEG figure deserves its own explanation, because the obvious objection is a good one: no formulator I know adds polyethylene glycol to an ink. Carriers are water, witch hazel, glycerin, alcohol, and sometimes propylene glycol. So why is it in a third of the bottles?

Because it isn't going in as a carrier. It's going in as a binder and dispersant, and it arrives attached to the pigment rather than being poured into the mix. A 2023 review of tattoo hypersensitivity lists polyethers, naming poloxamer and polyethylene glycol, among the standard binding agents used to hold pigment particles together and to the needle, and notes plainly that declaration of binders is routinely missing from tattoo ink labels. Pigment-dispersion patents describe the same chemistry, using PEG chain segments as reactive dispersants that bond to the surface of oxide pigments.

So the ink maker may never have handled PEG as a raw material. It came in with the dispersion, from a supplier further upstream, and nobody wrote it down. That is a different problem from concealment, and arguably a harder one to fix.

Three chemicals get confused here, and the names are the reason. Polyethylene is the plastic a bottle is made from. Polyethylene glycol is a water-soluble polyether made from ethylene oxide. Ethylene glycol is antifreeze, and toxic. A polyethylene bottle does not leach PEG, so packaging is not the explanation.

The researchers also anticipated the obvious methodological objection. PEG is a common background contaminant in MALDI-TOF instruments, so they re-ran freshly prepared samples specifically to confirm the PEG was in the ink rather than in the machine.

On what it means: popular coverage of the US study ran headlines about organ damage and kidney failure. The study's own lead author was more measured, telling Chemical & Engineering News that a missing ingredient is not a major health concern, but that it still represents a failure of the manufacturing and labeling process. That is the right register for this. The problem is that nobody knows what is in the bottle, not that PEG is poisoning anyone.

The same US analysis also found undeclared propylene glycol in 15 inks, and propylene glycol was the American Contact Dermatitis Society's Allergen of the Year in 2018. The one most of us do use is also the one with an allergy record.

Looking up the brands in the studies

Both papers name manufacturers. I would rather you compare the products on your shelf with the scientists' tables than rely on a list copied into this article.

The 2021 survey lists nine named brands in its methods section and then reports results brand by brand. Its Table 1 breaks down which manufacturer failed which labeling requirement: manufacturer address, durability date, sterility guarantee, batch number, correct ingredients, with pass/fail counts for each brand. Later figures plot copper, chromium, nickel, lead and barium content by brand. It records that only a handful of individual inks, from two named companies, were free of any labeling violation. It also records that one named brand's bottles carried identical ingredient lists across every color, declaring only a white and a black pigment for products that were plainly neither, and the authors concluded those labels were completely unreliable.

That paper is open access. You can read every table without paying for it.

The 2024 US analysis names manufacturers too and discusses specific products by name where its measurements disagreed with the label.

Follow the citations. Look up the inks on your own shelf. You will form a better opinion from the primary data than from anything I could tell you, and you won't have to take my word for any of it, which is the point.

My view.
I assumed for years that the secrecy exists to keep dangerous ingredients out of public view. Having gone through the regulations and the analytical surveys for this article, I think the simpler explanation is worse.
A deliberate secret implies somebody knows the real number. The data is more consistent with companies not fully knowing what they are selling: pigment passes through several hands before it reaches an ink maker, and the sheet reflects what somebody upstream said rather than what was measured. Errors running in both directions fit that picture better than they fit a coordinated motive. The PEG finding is the clearest example I know of.
I can't prove either reading, and nothing above depends on which is true.

What I found comparing safety sheets

The same manufacturers who publish minimal US sheets publish European sheets with color index numbers, CAS numbers and percentage bands, because a regulator there requires it.

I've compared them side by side for the same product line. The US sheet said "organic pigment, distilled water, witch hazel, alcohol" and declared the product non-hazardous. The EU sheet for another color from the same company listed the pigment's CI number, its CAS number and its percentage range, plus the preservative and trace chromium.

The information exists. It appears when someone asks with authority.

What to do with this

If a manufacturer sells into Europe, ask for its EU-format SDS alongside the US sheet. Get CI and CAS numbers for the specific color, and ask what the dispersion package contains. The ink maker may need information from its own pigment supplier to answer that.

Ask for a batch certificate of analysis too. The safety sheet describes the formula; a batch result describes the lot tested. Read the hazards even when an identity is withheld, and question how a 'non-hazardous' classification was established.

Record the lot used for each client. If the label later proves wrong, those records are the trail back to the bottle.

None of this requires you to distrust your supplier. It requires you to ask questions a good supplier can answer. I cover what those answers should look like in my checklist for a safer tattoo ink, what a bottle actually contains in what's actually in tattoo ink, and what the pigments do in skin in my article on ink ingredient interactions.