Correction

“PPD-Free” Is Not the Same as Hypoallergenic

The claim

“If hair dye brings me out in a rash, a PPD-free box is the safe one.”

The short answer

Probably not. The EU files toluene-2,5-diamine — the usual PPD substitute — under the same phenylenediamine warning block, at the same 2% free-base cap after mixing. The regulation's own labelling choice contradicts the marketing.

Evidence status

Settled

The Cosmetic Record · Published 2026-08-06 · Last checked 2026-08-06 · 18 sources · Corrections: none

1. What the allergy is: a delayed reaction to the amine and its oxidation intermediates

Allergic contact dermatitis from hair colour is a type IV reaction — cell-mediated and delayed, appearing hours to days after contact rather than within minutes. That lag is why the diagnostic test for it is a patch read at 48 and 72 hours rather than a prick test read immediately.

The sensitising material is not only the amine as supplied. In an oxidative colourant the primary intermediate is oxidised by alkaline hydrogen peroxide, and the product of that oxidation couples with a second molecule into the pigment that stays in the fibre. Which species does the work is still argued: the standard review of the chemistry lists both p-benzoquinone diimine and its conjugate acid, the diiminium ion, as proposals for p-phenylenediamine, and records that the self-coupling products called Bandrowski's bases form when no coupler is present but are believed not to form inside the hair.⁵ Sensitisation can be to the parent amine or to a reactive oxidation product, which is one reason a person who reacts to one member of the family often reacts to its relatives.

The European Commission's Scientific Committee on Consumer Safety has catalogued how strong each of these sensitisers is. Its 2013 memorandum sorts the classified hair dye substances into extreme, strong and moderate: p-phenylenediamine is extreme, with a local lymph node assay EC3 of 0.06 %, and toluene-2,5-diamine is extreme as well, at 0.31 %.² (An EC3 is the concentration estimated to triple lymph-node cell proliferation in a mouse assay — a laboratory potency ranking, not a human dose.) The committee concluded that substances meeting the classification criteria “may not be safe for consumers and that this is particularly so for hair dye substances categorised as extreme and strong sensitizers”. In a Polish series of 4,087 patients patch-tested for allergic contact dermatitis between 2006 and 2015, 166 — 4.1% — reacted to p-phenylenediamine or a related amine.⁴

2. What the EU box must say, quoted in full

Annex III of Regulation (EC) No 1223/2009 is a restricted list: a substance in it may be used only for the stated purpose, only up to the stated concentration, and only with the stated wording printed on the pack. Entry 8a covers p-phenylenediamine and its salts as a hair dye substance in oxidative products, and caps it — general and professional use alike — at 2% calculated as free base after mixing. This is the block that must appear:

Hair colourants can cause severe allergic reactions.
Read and follow instructions.
This product is not intended for use on persons under the age of 16.
Temporary “black henna” tattoos may increase your risk of allergy.
Do not colour your hair if:
— you have a rash on your face or sensitive, irritated and damaged scalp,
— you have ever experienced any reaction after colouring your hair,
— you have experienced a reaction to a temporary “black henna” tattoo in the past.
Contains phenylenediamines.
Do not use to dye eyelashes or eyebrows.

Two things in that block are worth holding on to. It is an unconditional warning that the product class can cause severe allergic reactions — not a warning triggered by a particular ingredient's presence above a threshold. And it does not tell anyone to test the product on themselves first.

3. PTD is under the same warning, and the regulation's own wording proves it

The substance put forward as the alternative to p-phenylenediamine is toluene-2,5-diamine, also written as 2,5-diaminotoluene or PTD, and listed in ingredient declarations as TOLUENE-2,5-DIAMINE or TOLUENE-2,5-DIAMINE SULFATE. The American Contact Dermatitis Society named its sulfate salt Allergen of the Year for 2025 on exactly that footing: a substance with a “dual role as both an allergen and an alternative for some PPD-allergic individuals”.⁶ It has its own Annex III entry, 9a, with CAS 95-70-5 and EC 202-442-1. After mixing under oxidative conditions it must not exceed 2,0 % calculated as free base, or 3,6 % calculated as the sulfate salt — the same ceiling, in free-base terms, as p-phenylenediamine.¹

The warning block on entry 9a is the entry-8a block, sentence for sentence: the same statement that hair colourants can cause severe allergic reactions, the same line that the product is not intended for anyone under 16, the same black-henna sentence, the same “Do not colour your hair if” list. Exactly two clauses differ. The first is a detail of scope: entry 8a's general-use block closes “Do not use to dye eyelashes or eyebrows.”, entry 9a's closes “Do not use to dye eyelashes.” — entry 9a carries a second limb permitting professional eyelash colourants, and its general-use limb says nothing about eyebrows either way. The second difference is the decisive one. Where an entry-8a product declares “Contains phenylenediamines.”, an entry-9a product declares:

Contains phenylenediamines (toluenediamines)

The drafting is not ambiguous: toluene-2,5-diamine is labelled a phenylenediamine, family name first and sub-family in brackets. The neighbouring entry 9 does the same for the whole class, restricting “Methylphenylenediamines, their N-substituted derivatives and their salts” with the identical parenthetical.

The clinical literature points the same way. In a Dutch series of 8,036 patients patch tested with the European baseline series, 251 were sensitised to p-phenylenediamine or toluene-2,5-diamine or both: 231 to PPD and 109 to TDA, which leaves 89 reacting to both. The authors concluded that cross-reactivity “was commonly found among individuals sensitized to PPD or TDA, and was strongly related to the strength of the patch test reaction”.³

Whether the claim is even true of the box has been measured. A New York University group ran 51 best-selling US hair dyes marketed as “PPD-free” through high-performance liquid chromatography coupled to high-resolution mass spectrometry. Seven contained a compound absent from the ingredient list; five contained p-phenylenediamine itself with no mention of it on the list, four of those carrying a “PPD-free” label, and one held more than 2% PPD by weight.⁷

An accurate “PPD-free” claim is still not a claim about allergy — it is a statement about one annex entry. Regulation (EU) No 655/2013, which sets the common criteria for cosmetic claims in the EU, requires claims to be supported by adequate and verifiable evidence and bars those conveying “the idea that a product has a specific benefit when this benefit is mere compliance with minimum legal requirements”.¹⁸ Nothing in it converts “PPD-free” into “safe for a person who reacts to hair dye”.

4. The American answer: the coal-tar carve-out and the exact caution it demands

The United States has no annex, no concentration limits for these substances and no positive list for them. It has one sentence. Section 601(a) of the Federal Food, Drug, and Cosmetic Act deems a cosmetic adulterated if it contains a poisonous or deleterious substance that may render it injurious — and then exempts coal-tar hair dye from that provision entirely, on two conditions:

Caution-This product contains ingredients which may cause skin irritation on certain individuals and a preliminary test according to accompanying directions should first be made. This product must not be used for dyeing the eyelashes or eyebrows; to do so may cause blindness.

“Coal-tar” is a historical term rather than a description of the raw material: FDA's page records that the colours were once by-products of the coal industry, are now mostly made from petroleum, and that the category covers permanent, semi-permanent and temporary hair dyes.¹¹ Section 601(e) then exempts coal-tar hair dyes from the colour-additive approval requirement that applies to every other colour in a cosmetic.⁸ The Modernization of Cosmetics Regulation Act of 2022 did not close the carve-out. It added a general duty to hold adequate substantiation of safety — and then, at FD&C §608(b), 21 U.S.C. 364d(b), disapplied that duty to “coal-tar hair dye that otherwise complies with the requirements of section 361(a)”, leaving only an obligation to keep safety records.⁹

Two American details are frequently misreported. The cancer warning at 21 CFR 740.18 has never taken effect: the effective-date note printed under the section records that at 47 FR 7829, 23 February 1982, it “was stayed until further notice”, and the stay is still there.¹⁰ And lead acetate was delisted by a rule published 31 October 2018 that took effect only on 6 January 2022, after an objection stayed it.¹⁴

As for the word in this article's headline: FDA states that “There are no Federal standards or definitions that govern the use of the term ‘hypoallergenic’”, that manufacturers need not submit substantiation for such claims, and that a 1977 appellate decision struck down the regulation that would have defined it.¹² A “PPD-free” claim is a narrower cousin of the same move.

5. Brazil: Grau 2, notified rather than registered, with the prova de toque mandated

Brazil classifies personal-care products by risk. Hair dye is Grau 2, the higher of the two grades, listed at item II nº 45 of Anexo I to RDC 907/2024 as “Tintura capilar temporária, progressiva ou permanente” — that annex as replaced by RDC 949/2024. Grau 2 is a risk grade, not a registration status. Art. 34 lists the nine groups that must go through registro; hair dye is not among them, and the closest item, IV, is “produto para alisar e tingir os cabelos”, a product that straightens and colours. Under Art. 35 everything off that list is exempt from registration and goes through comunicação prévia — so ordinary hair colour is notified, not registered.¹⁵ The gap between those two words is the single most misread thing in Brazilian cosmetic labelling, and it has its own article here.

What Brazil does require, and the EU does not, is an instruction to test:

CUIDADO. Pode causar irritação na pele ou reação alérgica. Antes de usar, fazer a prova de toque (descrever);
Em caso de contato com os olhos, lavar com água em abundância;
Manter fora do alcance das crianças;
Não aplicar se o couro cabeludo estiver irritado ou lesionado; e
Não usar nos cílios.

Since 11 June 2026 Brazil also has a substance annex shaped like the European one. RDC 1.029/2026 internalises MERCOSUR resolution GMC nº 06/25, capping p-phenylenediamine at entry 8b at 2% as free base after oxidative mixing and toluene-2,5-diamine at entry 9b at 2,0 % free base or 3,6 % as the sulfate, with the label line “Contém fenilenodiaminas (diaminotoluenos)”. The entry numbers differ from the EU's; the limits and the warning do not. Art. 2 gives products already regularised 24 months to comply, so Brazilian stock before June 2028 may still be built to the previous list.¹⁶

6. Two regulators, two opposite answers on consumer patch testing

The United States makes the consumer self-test the price of the exemption: no adequate directions for a preliminary test, no carve-out. Brazil orders the same thing in its own words and requires the method to be described. The European Union, asked whether such a test should be put in consumers' hands, declined.

The Scientific Committee on Consumer Safety examined a standardised Allergy Alert Test in 2019 and found that its diagnostic performance showed “a very good specificity, but a potentially moderate sensitivity, leaving room for the possibility of false-negative AAT reactions in sensitised consumers who may then experience allergic contact dermatitis to a subsequently applied product”, and that it “cannot, at this stage, endorse the use of the AAT as an ‘alert’ for contact allergy to hair dyes in consumers”. It added a second objection: the test “carries the same basic risk of sensitisation as the use of a hair dye product by a consumer”, so if it “is used on a regular basis before hair dyeing, it will inevitably increase the number of exposures, and this may increase the risk of sensitisation”.¹⁷

Three jurisdictions looked at the same procedure and produced two opposite answers about whether to require it. That disagreement is itself a fact about the state of the evidence.

7. Black henna, and why the regulation names it

The EU warning block singles out one product that is not a hair dye at all: “Temporary ‘black henna’ tattoos may increase your risk of allergy.” Henna itself, from Lawsonia inermis, stains reddish-brown. To make a black, fast-developing skin stain, something else is added, and FDA states that the additive “is often a coal-tar hair dye containing p-phenylenediamine (PPD)”, that an artist may use a PPD-containing hair dye on its own, and that “By law, PPD is not permitted in cosmetics intended to be applied to the skin”. Henna is approved in the US only as a hair dye, so mehndi products containing it are adulterated.¹³

The relevance to a box of hair colour is exposure history. A holiday temporary tattoo is a high-concentration, long-contact, occluded application of the same chemistry, and it is a route by which someone may become sensitised years before opening a dye carton. That is why the sentence sits in the Annex III block, and why it appears in the Brazilian annex too.

8. What a patch test can and cannot rule out

A negative home test is evidence about one product, on one occasion, at one site, read once. It is not a property of the person. FDA's own hair dye page makes the limits explicit: “People can develop sensitivities with repeated exposure. In addition, formulations may change over time. So, it's possible to have a reaction even if you have dyed your hair in the past, without a problem.”¹¹ Sensitisation is acquired, and the acquiring event is usually an ordinary use of the product.

Add the SCCS finding on sensitivity and the failure mode is clear: a test with good specificity and moderate sensitivity produces few false alarms and a meaningful number of false reassurances. A positive result is informative. A negative one is weak evidence, and it expires when the formula changes.

Which leaves the narrow conclusion. “PPD-free” identifies one Annex III entry that is absent. It says nothing about entry 9a, nothing about entry 9, and nothing about the other primary intermediates the same committee classifies as strong sensitisers — among them N,N-bis(2-Hydroxyethyl)-p-phenylenediamine sulfate and Hydroxyethyl-p-phenylenediamine sulphate.² The ingredient declaration on the pack, read against the annex entries, carries information the front-of-pack claim does not. What a given person actually reacts to is a clinical question, and patch testing by a dermatologist is how it is answered.