Toluene-2,5-Diamine Sulfate
Also known asPTD, p-Toluenediamine sulfate, 황산톨루엔-2,5-디아민
FunctionOxidative dye — PPD-class allergen
What it is — Toluene-2,5-Diamine Sulfate (also written p-toluenediamine sulfate, or PTD) is a primary intermediate in permanent oxidative hair colour. It sits in the same para-phenylenediamine chemical family as PPD and is frequently used as the substitute when a brand formulates without PPD by name.
What it does — In a two-part dye it reacts with couplers such as resorcinol and the aminophenols under a peroxide developer, forming large colour molecules inside the hair shaft. This is what produces permanent, one-application grey coverage rather than a surface tone that washes out.
Typical use — Permanent hair colour and colour shampoos, at low percentages capped by regulation. In Korea it is a restricted-use hair-dye ingredient; in the EU it is likewise permitted only in hair colour products, within concentration limits and with mandatory allergy warnings.
Who it suits / good to know — Because it is a PPD-family compound, it is a well-documented cross-reactant: a person who reacts to PPD should assume they may react to this as well. A product can be truthfully labelled PPD-free and still contain it. If you have ever had a reaction to hair dye — itching, swelling, weeping or a rash on the scalp, hairline or ears — this is the ingredient class to raise with a dermatologist before using a product that contains it.
Safety — DHALIORA grades it high risk: a PPD-class oxidative dye and a frequent sensitizer with known cross-reactivity. This reflects the ingredient in general and is not medical advice. Always patch-test 48 hours before every use, and never use it on eyebrows or lashes.
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