"A practical supplier guide to Azelaic acid (CAS 123-99-9): what the dicarboxylic acid is, how its comedolytic, antimicrobial, anti-inflammatory, and tyrosinase-inhibiting actions clear acne, calm rosacea, and fade marks, typical up-to-10% use levels, smart pairings with salicylic acid, kojic acid, alpha-arbutin, vitamin C, GHK-Cu, squalane, mild surfactants, citric acid and Argireline, plus safety notes and buyer COA guidance."
-Deshangchemical-chemechemi
Azelaic Acid (CAS 123-99-9): The Dicarboxylic Acid That Calms Acne, Rosacea, and Stubborn Marks
If you formulate for problem skin, you already know the usual suspects — salicylic acid for pores, niacinamide for tone, retinoids for renewal. What often gets left out of that conversation is azelaic acid, listed on our product page under CAS 123-99-9. It is one of the few actives that quietly covers three jobs at once: it clears breakouts, it takes down the redness of rosacea, and it fades the dark marks acne leaves behind. For a private-label or contract manufacturer, that combination is why it keeps earning shelf space next to the better-known acids.
What the material actually is
Azelaic acid is a saturated dicarboxylic acid — nine carbons, two acid groups at the ends. That structure is the reason it behaves the way it does: it is water-soluble enough to build into a serum or gel, yet it also has an affinity for the lipid-rich environment of the follicle. The spec sheet on our product page carries the data a buyer checks before quoting or sampling:
| CAS | 123-99-9 |
| Molecular formula | C9H16O4 |
| Molecular weight | 188.22 |
| EINECS | 204-649-9 |
| Melting point | 106–109 °C |
| Appearance | white to off-white crystalline powder |
| Solubility | slightly soluble in cold water (~1 g/L at 25 °C), freely soluble in ethanol, ether and hot water |
| Density | ~1.03 g/cm³ |
| pKa | ~4.5 |
| Storage | room temperature, sealed, dry |
It arrives as a fine white-to-off-white crystalline powder. Unlike peptides or some enzymes, it is stable at room temperature and needs no cold chain — a real logistical advantage when you are moving drums or bags through a normal warehouse rather than a refrigerated one. Keep it sealed and dry and the assay holds.
How it works on skin
Azelaic acid is not a single-mechanism ingredient, and that is exactly why formulators like it. First, it is comedolytic: it normalizes the way keratinocytes shed inside the follicle, so the pore is less likely to clog in the first place. Second, it is antimicrobial against Cutibacterium acnes (the bacterium tied to acne) without wiping out the whole skin flora the way a broad antibiotic can. Third, it carries a measurable anti-inflammatory effect, which is why it is one of the few actives with a formal place in managing rosacea — it reduces the papules and pustules that define that condition.
On top of those three, azelaic acid is a competitive inhibitor of tyrosinase, the enzyme that drives pigment production. That gives it a mild brightening action that shows up most clearly on post-inflammatory hyperpigmentation and melasma. A single active that addresses the blemish, the redness around it, and the shadow it leaves is rare, and it is the main reason the ingredient sits comfortably in both acne and pigmentation routines.
Where it goes in the formula
Use levels are well established. Prescription products run at 15–20% (the 15% foam and 20% cream you see on pharmacy shelves), while cosmetic leave-on products are typically built around 10% or below. The European SCCS opinion regards azelaic acid as safe up to 10% in leave-on cosmetic products, which is the band most brands work in. It is stable across the mildly acidic to neutral pH range, and it pairs cleanly with the acids and humectants already in a routine.
Because it is only slightly soluble in cold water, most stable systems dissolve it in a cosolvent such as propylene glycol or ethanol, or build it into an emulsion. A small amount of Citric Acid Anhydrous (CAS 77-92-9) is the clean way to set and hold the pH of the water phase without adding color or odor, and it doubles as a chelator that keeps the formula stable over its shelf life.
Pairing it with other actives
Azelaic acid rarely carries a formula alone, and it is forgiving about what sits next to it. The natural companions cover the rest of the clarifying-and-brightening story:
- Salicylic Acid (CAS 69-72-7) — the oil-soluble BHA that clears the pore from the inside, while azelaic acid works on the redness and the mark; together they address both the clog and its aftermath.
- Kojic Acid (CAS 501-30-4) and Alpha-Arbutin (CAS 84380-01-8) — two established tyrosinase inhibitors that reinforce azelaic acid's brightening angle for post-acne and sun-related discoloration.
- L-Ascorbic Acid (CAS 50-81-7) — vitamin C antioxidant support that protects the formula and helps even tone alongside the dicarboxylic acid.
- GHK-Cu Copper Peptide (CAS 49557-75-7) — a signal peptide aimed at repair and firmness, useful in a post-breakout recovery step.
- Squalane (CAS 111-01-3) — the emollient carrier that cushions the skin and offsets any tightness from an active treatment.
- Sodium Lauroylsarcosinate (CAS 137-16-6) — a mild amino-acid surfactant for the cleanser that precedes an azelaic acid treatment.
- Argireline (CAS 616204-22-9) — an anti-wrinkle peptide for a leave-on product that pairs clarifying and anti-aging in one step.
Handling, storage, and safety notes
The powder is low acute toxicity by mouth (oral LD50 greater than 5 g/kg in rats) and it is not classified as a reproductive toxin, which is one reason it is considered appropriate for use during pregnancy where many other acne actives are not. In the lab, handle it as a mild dust: avoid breathing it in, keep it away from the eyes, and wash any contact off promptly. Because it is only slightly soluble in cold water, spills are easy to wipe up rather than smear. Store the sealed material at room temperature away from moisture.
For finished goods, match the concentration to the claim and the market. Up to 10% is the comfortable cosmetic leave-on band in the EU; higher strengths move the product into the dermatological or prescription space and change the documentation you need. As with any active, a patch test and a stable, well-buffered base make the difference between a product that performs and one that just lists the ingredient.
What to check before you buy
When you request a quote, ask for the COA (identity, assay, heavy metals, microbiology), pack size, and lead time. For cosmetic- and pharma-grade supply you want a supplier who can show consistent assay, low residual solvent, and batch traceability, plus the documentation your QA team needs for a finished-product filing. Beyond skincare, the same CAS feeds lubricating-fluid and plastic precursors, so grade and impurity profile matter for the end use.
For the active itself, see the Azelaic acid product page for current assay, pack size, and COA details. If you are building an acne, rosacea, or pigmentation line and want to discuss use levels, solubilization, or a paired acid-plus-peptide system, our team can help you spec the combination.
