What it is
The register’s chemical name for it: “2-Amino-3-hydroxybutanoic acid.”
- EU register name (INCI)
- THREONINE
- CAS number
- 72-19-5 / 80-68-2
- EC number
- 200-774-1 / 201-300-6
What the register lists it for
These are the uses the European Commission’s CosIng register lists for Threonine in any cosmetic, hair roles first. They say why a maker might add it, not what it does in one formula, and they aren’t a safety rating.
- Hair conditioning
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The register’s hair role for ingredients that make hair feel softer, smoother or easier to comb. Most conditioners, masks and leave-ins list several.
Register definition: “Enhancing the appearance and feel of hair. Leaving the hair easy to comb, supple, soft and shiny and/or imparting volume, lightness, gloss, texture, etc.”
- Hair waving or straightening
-
The register’s role for ingredients that can change the hair’s structure in a perm or relaxer. None of the products here is a perm or relaxer; an ingredient with this role is usually on their labels for another listed use.
Register definition: “Modifying the chemical structure of the hair, allowing it to be set in the style required (permanent waves or hair straightening).”
- Antistatic
-
Cuts the static that makes dry hair fly away. Many conditioning ingredients carry this role too, because both work at the hair’s surface.
Register definition: “Preventing and/or reducing static electricity by neutralising electrical charge on surfaces.”
Where it sits on each label
US labels list ingredients from most to least, except that those at 1% or less may follow in any order. A name near the top is a large part of the formula. A label doesn’t mark where the 1% point falls, so further down, the order says little about how much is in it.
- Shampoos 1 label First five names: 0 of 1 Shampoos without it
- Clarifying shampoos 1 label First five names: 0 of 1 Clarifying shampoos without it
- Rinse-out conditioners 2 labels First five names: 0 of 2 Rinse-out conditioners without it
- Deep conditioners 1 label First five names: 0 of 1 Deep conditioners without it
Every label, product by product (5)
- Kristin Ess Moisture Rich Curl Shampoo Shampoo 20th of 41 names
- OLAPLEX No.4C Bond Maintenance Clarifying Shampoo Clarifying shampoo 23rd of 55 names
- Kristin Ess Moisture Rich Curl Conditioner Rinse-out conditioner 16th of 41 names
- Cécred Hydrating Conditioner Rinse-out conditioner 30th of 50 names
- Innersense Organic Beauty Hydrating Hair Mask Deep conditioner 36th of 54 names
Each line runs from the first name on a label to the last; a dot is where this ingredient sits. Makers change formulas now and then; if the list on your bottle differs, go by your bottle.
Your next step
Other hair conditioning ingredients on these labels
- Glycerin 131 labels
- Panthenol 72 labels
- Cocos Nucifera (Coconut) Oil 69 labels
- Behentrimonium Methosulfate 38 labels
- Caprylyl Glycol 37 labels
- Behentrimonium Chloride 34 labels
- Cocamidopropyl Betaine 34 labels
- Simmondsia Chinensis (Jojoba) Seed Oil 34 labels
Updated · The name, numbers and uses come from the European Commission’s CosIng entry (CC BY 4.0); we write the uses in US spelling and put the hair ones first. The labels are each maker’s own. The order rule is the FDA’s Cosmetics Labeling Guide. All our sources are on the Sources page.