New to formulating with Azelaic Acid?
Azelaic Acid can be tricky to work with because it is poorly soluble in water. Our simple guide explains why water, solvents and pH matter, how Azelaic Acid becomes available to the skin, and why the delivery system can be just as important as the percentage you use.
Read: Why Water Matters in an Azelaic Acid Serum →
INCI: Azelaic Acid
CAS No.: 123-99-9
Appearance: White crystalline powder
Solubility: Poorly soluble in water; requires an appropriate solvent, dispersion or delivery system
Typical Cosmetic Use Level: 5–10%
Formulation Type: Water-based gels, gel-serums, emulsions, suspensions and specialist solvent systems
Azelaic Acid is a multifunctional skincare active particularly valued in formulations designed for blemish-prone skin, uneven-looking skin tone, post-blemish marks and visible redness.
Unlike many cosmetic actives, however, Azelaic Acid is not simply added to water and stirred until dissolved.
Its naturally low water solubility makes the formulation vehicle just as important as the percentage of Azelaic Acid used.
For formulators, this makes Azelaic Acid particularly interesting: the challenge is not simply getting Azelaic Acid into the bottle, but creating a system that keeps enough of the active available so that it can ultimately leave the formula and interact with the skin.
Azelaic Acid at a Glance
| INCI | Azelaic Acid |
| CAS | 123-99-9 |
| Appearance | White crystalline powder |
| Ingredient Type | Dicarboxylic acid |
| Typical Use Level | 5–10% |
| Water Solubility | Poor |
| Oil Solubility | Very limited |
| Preferred Formulation Approach | Solvent system, emulgel, gel-serum or controlled suspension |
| Suggested Formulation pH | Approximately 4.5–5.5 depending on the complete formulation |
| Skin Types | Oily, combination, blemish-prone and uneven-looking skin |
Why Formulators Use Azelaic Acid
Azelaic Acid is unusual because it can address several common cosmetic concerns within one formulation.
Uneven-Looking Skin Tone
Azelaic Acid is widely used in formulations intended to improve the appearance of uneven tone and post-blemish discolouration.
This makes it particularly interesting alongside other tone-supporting ingredients such as:
Alpha Arbutin
Tranexamic Acid
Niacinamide
4-Butylresorcinol
Each works through a different formulation and skin pathway, allowing more sophisticated multi-active products to be developed.
Blemish-Prone Skin
Azelaic Acid is especially associated with skincare for oily and blemish-prone complexions.
It can be incorporated into lightweight gels, gel-creams and targeted serums without requiring the heavy oil phase associated with some traditional active ingredients.
Visible Redness
Azelaic Acid is also frequently selected for formulations designed for skin that appears red, reactive or uneven.
For this reason, it can work particularly well in minimalist formulations where the aim is to combine effective actives with a relatively simple base.
Skin Texture
Azelaic Acid is often used in products intended to support a smoother, clearer-looking skin surface.
It therefore fits particularly well into products designed for:
- uneven skin texture
- congestion-prone skin
- visible post-blemish marks
- combination skin
- mature skin experiencing uneven pigmentation
The Most Important Thing to Understand About Azelaic Acid
10% in the bottle does not automatically mean 10% is available to the skin.
Azelaic Acid is poorly soluble in ordinary water.
If 10 g of Azelaic Acid powder is simply mixed into 90 g of water, most of it will remain as undissolved particles.
Those particles do not simply pass through the skin as crystals.
For Azelaic Acid to become readily available, molecules first need to be dissolved or effectively released from a well-designed dispersion system.
That is why the choice of:
solvent + water content + pH + formulation structure
can be extremely important.
Why Use a Solvent?
Cosmetic solvents can help separate Azelaic Acid molecules from the crystalline powder and keep more of the ingredient available within the formulation.
Possible formulation solvents and co-solvents include:
1,3-Propanediol
A versatile cosmetic humectant and solvent that can be particularly interesting for Azelaic Acid formulations.
Higher concentrations may be required when attempting to solubilise substantial quantities of Azelaic Acid.
Propylene Glycol
Another commonly used polar glycol capable of improving the solubility of difficult-to-dissolve ingredients.
Dimethyl Isosorbide – DMI
A specialist cosmetic solvent particularly useful when developing advanced active-delivery systems.
DMI may be used as part of a wider solvent system rather than automatically replacing water or glycols.
Ethoxydiglycol
A highly polar cosmetic solvent that can also be explored when developing difficult active formulations.
Solvent Choice Is About More Than Solubility
It can be tempting to search for the solvent that dissolves the largest possible amount of Azelaic Acid.
But good topical formulation is more subtle than that.
The active eventually needs to:
Dissolve in the vehicle
↓
Remain available
↓
Reach the skin surface
↓
Leave the vehicle
↓
Partition into the skin
A solvent therefore needs to help Azelaic Acid enter the formulation without necessarily holding onto it so strongly that release becomes inefficient.
This is one reason formulation testing is so important.
Why Add Water If Azelaic Acid Is Poorly Water Soluble?
Water is not necessarily just filler.
Once water is present, Azelaic Acid can exist in a balance between neutral and ionised forms.
In very simple terms:
Neutral Azelaic Acid ⇄ Charged Azelaic Acid
The balance between these forms is influenced by pH.
The charged form generally prefers the aqueous environment, while the neutral form may partition more readily toward the lipid-rich outer layers of the skin.
A carefully designed water + solvent system can therefore help balance:
Solubility
with
Skin availability
Water also hydrates the outermost layer of the skin, creating a different delivery environment from a completely anhydrous serum.
This is why a well-designed:
Azelaic Acid + Propanediol + Water
gel-serum can potentially be a very effective and surprisingly simple formulation.
How to Use Azelaic Acid in Formulation
Azelaic Acid can be formulated in several different ways.
Method 1 – Solvent-Based Gel Serum
Azelaic Acid may be solubilised or partially solubilised using a substantial solvent phase such as 1,3-propanediol.
Water and a compatible gel-forming polymer can then be incorporated to create a lightweight serum.
This approach gives the formulator control over:
- solvent concentration
- pH
- active availability
- skin feel
- viscosity
Method 2 – Emulsion Gel / Emulgel
Azelaic Acid can be incorporated into a lightweight emulsion-gel containing:
water phase
solvent system
small oil phase
emulsifier
gel network
This can provide a more elegant skin feel than a very high-glycol serum while allowing the formulator considerable control over active delivery.
Method 3 – Controlled Suspension
Not every Azelaic Acid formulation needs to be completely transparent or molecularly dissolved.
Azelaic Acid can also be formulated as a fine, controlled suspension.
In this system, part of the active remains as microscopic solid particles.
As dissolved Azelaic Acid leaves the vehicle, additional material may gradually dissolve from this reservoir.
Particle size, dispersion quality and crystallisation control become particularly important in this type of formulation.
Don't Confuse Dispersion With Dissolution
This is one of the most common mistakes when working with Azelaic Acid.
If a white powder disappears temporarily when homogenised into a cream, that does not necessarily mean it has dissolved.
It may simply have been dispersed very finely.
Dissolved
Individual Azelaic Acid molecules are distributed through the solvent.
Dispersed
Small solid Azelaic Acid particles remain suspended throughout the product.
Both approaches can potentially be used successfully.
But they are not the same delivery system.
What About Heating?
Heating may significantly improve the rate at which Azelaic Acid dissolves in some solvent systems.
However:
Something that dissolves when hot may crystallise again when the formulation cools.
Always evaluate the finished formulation after cooling rather than judging solubility while the mixture is hot.
For experimental formulations, monitor for:
- crystals appearing after cooling
- sediment
- gritty texture
- changes after 24–48 hours
- recrystallisation after several weeks
- changes during hot/cold stability testing
Recommended Formulation pH
For aqueous formulations, a useful development region is approximately:
pH 4.5–5.5
The exact target should depend on the complete formulation and the other ingredients being used.
With Azelaic Acid, pH influences more than product acidity.
It affects the balance between neutral and ionised Azelaic Acid, which in turn can influence solubility and availability.
Do not automatically assume that:
lower pH = better Azelaic Acid delivery.
Formulation behaviour is more complex.
Ingredients That Work Particularly Well With Azelaic Acid
For Uneven Tone
Alpha Arbutin
Water-soluble brightening active suitable for multi-pathway tone formulations.
Tranexamic Acid
Interesting for products targeting the appearance of stubborn uneven pigmentation.
Niacinamide
A versatile ingredient for barrier support, oiliness and uneven-looking skin.
4-Butylresorcinol
A highly targeted tone-supporting ingredient for advanced formulations.
For Blemish-Prone Skin
Niacinamide
Particularly useful for combination and oily skin formulations.
Zinc PCA
Useful in lightweight products designed for oily and blemish-prone skin.
For Sensitive or Red-Looking Skin
Ectoin
Helps support hydration and skin resilience.
Bisabolol
Oil-soluble soothing ingredient particularly suitable for sensitive-skin formulations.
For More Advanced Delivery Systems
1,3-Propanediol
Solvent + humectant.
Dimethyl Isosorbide – DMI
Specialist cosmetic solvent.
Pentylene Glycol
Humectant and multifunctional formulation ingredient.
Example Product Concepts
Azelaic Acid does not have to mean another thick white cream.
It can be explored in much more interesting formats.
Azelaic Acid Clear-Feel Gel Serum
A minimalist glycol/water delivery system with a lightweight gel texture.
Azelaic Acid + Alpha Arbutin Tone Serum
Combines two very different active approaches within one formulation.
Azelaic Acid Barrier Gel-Cream
A lightweight emulsion combining Azelaic Acid with soothing and barrier-supporting ingredients.
Post-Blemish Treatment Serum
Azelaic Acid combined with Niacinamide and complementary tone-supporting ingredients.
Azelaic Acid + Ectoin Comfort Serum
A formulation concept balancing a high-performance active with hydration and skin-comfort ingredients.
Multi-Pathway Uneven Tone Serum
Azelaic Acid combined with carefully selected brightening actives working through complementary mechanisms.
Storage & Handling
Store tightly closed in a:
cool, dry place away from direct sunlight and moisture.
Avoid unnecessary exposure to humidity.
Always use clean, dry formulation equipment.
For experimental formulations, evaluate the finished product for crystallisation and physical stability rather than assuming that a freshly prepared formula will remain unchanged over time.
Formulation Note
Azelaic Acid is a formulation ingredient rather than a finished cosmetic product.
The final product should be properly formulated, stability tested and assessed for its intended use.
When formulating products for sale, the complete finished cosmetic product — not simply the individual raw material — must meet the applicable UK or EU cosmetic safety and regulatory requirements.
Avoid medicinal claims such as treating or curing acne, rosacea or other medical conditions when marketing a cosmetic product unless the product is appropriately authorised for that purpose.
Technical Documents
Where available, JustGlow provides supporting documentation for the supplied batch, including:
Certificate of Analysis (COA)
Safety Data Sheet (SDS)
Always check the documentation supplied for your particular batch before commercial formulation.
Frequently Asked Questions
Is Azelaic Acid water soluble?
Only to a limited degree.
It should not be treated like Alpha Arbutin, Niacinamide or Tranexamic Acid, which are considerably easier to incorporate into aqueous formulations.
A suitable solvent, suspension or specialist delivery approach is normally required when working at meaningful concentrations.
Can I simply add 10% Azelaic Acid to water?
No.
Most of the Azelaic Acid would remain undissolved.
A proper formulation strategy is required.
Can I dissolve Azelaic Acid in 1,3-Propanediol?
1,3-Propanediol can be a useful solvent for Azelaic Acid and is particularly interesting for concentrated glycol/water delivery systems.
The amount required depends on the total formulation and the intended Azelaic Acid concentration.
Always test for recrystallisation after cooling and during stability testing.
Why add water if propanediol dissolves the Azelaic Acid?
Because water changes the formulation environment.
It allows conventional pH control, influences Azelaic Acid ionisation, hydrates the skin surface and changes the way Azelaic Acid partitions between the vehicle and the skin.
The strongest solvent system is therefore not automatically the best delivery system.
Does Azelaic Acid need to be completely dissolved?
Not necessarily.
Commercially viable Azelaic Acid products can use sophisticated suspension and dispersion systems.
However, a suspension needs to be deliberately engineered.
Simply having undissolved powder sitting at the bottom of a serum is not the same thing.
Can Azelaic Acid be used in an oil serum?
Azelaic Acid has very limited solubility in conventional cosmetic oils.
Simply adding Azelaic Acid powder to squalane, CCT or another carrier oil is unlikely to create an effective molecular solution.
A specialist solvent or dispersion strategy would be required.
What percentage should beginners start with?
For experimental cosmetic formulation, 5% can be considerably easier to work with than immediately attempting 10%.
Higher active concentration places greater demands on the solvent and delivery system.
Is more Azelaic Acid always better?
No.
The percentage on the ingredient list tells only part of the story.
Solubility, particle size, vehicle, pH, crystallisation and release from the formulation can all influence how the finished product performs.
A thoughtfully designed 5% formulation may therefore be more interesting than a poorly designed formula containing 10% undissolved powder.
Why Choose JustGlow Azelaic Acid?
JustGlow supplies cosmetic ingredients for formulators who want to go beyond simply following a recipe.
Azelaic Acid is a perfect example.
It encourages you to think about:
solubility
pH
ionisation
delivery systems
skin partitioning
crystallisation
and formulation stability
Because modern skincare formulation is not simply about putting an impressive percentage on a label.
It is about understanding how an ingredient behaves inside the formula — and how to make that ingredient available when the formula reaches the skin.
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