What it is
The register’s chemical name for it: “Sodium 5-oxo-2-pyrrolidinecarboxylate.”
- EU register name (INCI)
- SODIUM PCA
- CAS number
- 28874-51-3
- EC number
- 249-277-1
What the register lists it for
These are the uses the European Commission’s CosIng register lists for Sodium PCA 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.”
- 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.”
- Humectant
-
Holds water in the product and on the surface it touches. Glycerin, honey and aloe are common humectants on curly-hair labels.
Register definition: “Retaining and/or preserving the moisture in a product during use.”
- Skin conditioning
-
The register’s broad role for ingredients that keep skin in good condition. On a hair label it often sits beside a hair role, or marks a plant oil or extract.
Register definition: “Maintaining the skin in good condition.”
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 2 labels First five names: 0 of 2 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
- Leave-in conditioners 1 label First five names: 0 of 1 Leave-in conditioners without it
- Protein treatments 1 label First five names: 0 of 1 Protein treatments without it
Every label, product by product (8)
- Kristin Ess Moisture Rich Curl Shampoo Shampoo 39th of 41 names
- OLAPLEX No.4C Bond Maintenance Clarifying Shampoo Clarifying shampoo 34th of 55 names
- Jessicurl Clarifying Shampoo Clarifying shampoo 12th of 19 names
- Kristin Ess Moisture Rich Curl Conditioner Rinse-out conditioner 20th of 41 names
- Cécred Hydrating Conditioner Rinse-out conditioner 32nd of 50 names
- Innersense Organic Beauty Hydrating Hair Mask Deep conditioner 26th of 54 names
- DevaCurl Leave-In Decadence Leave-in conditioner 26th of 39 names
- Briogeo Don't Despair, Repair! MegaStrength+ Rice Water Protein + Moisture Strengthening Treatment Protein treatment · listed as Sodium PCA* 32nd of 35 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.