Cos De BAHA Salicylic Acid BHA 4% Serum

Cos De BAHA Salicylic Acid BHA 4% Serum

This acne serum is formulated around Salicylic Acid and Niacinamide to clear breakouts and refine the look of pores.

Worth noting

Contains Lavandula Angustifolia Flower Extract, an EU-listed fragrance allergen.

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What's inside

Key Ingredients

Benefits

Concerns

Ingredients Explained

Emollient, Humectant, Skin Conditioning

Aloe Barbadensis Leaf Extract is a botanical extract pulled from the leaves of aloe vera and one of the most studied plant ingredients in cosmetics.

The inner leaf gel it comes from is mostly water (~99-99.5%) and the remaining fraction is made up of pretty good stuff: polysaccharides, vitamins, phenolics, and enzymes.

Its headline job is hydration.

The star polysaccharide in aloe, acemannan, is a humectant that retains moisture and helps reduce trans-epidermal water loss.

Aloe also has real soothing credentials; it contains anti-inflammatory compounds like bradykinase and C-glucosyl chromone that help calm irritation and redness.

On the repair side, lab work shows that acemannan wakes up your skin's repair cells (fibroblasts), prompting them to multiply and speed up healing.

There's some human data for cosmetic benefit too: a cream containing 10% Aloe Barbadensis leaf extract improved skin hydration and elasticity in a real-use study.

Safety-wise, this ingredient is well-regarded with just one rare downside; there have been some case reports of acute eczema, contact urticaria, and dermatitis in people who applied aloe-derived ingredients topically. Those with a known aloe or Liliaceae sensitivity should patch test.

Typical use levels range widely, from under 1% up to 90%+ depending on the format and the effect you are after.

Learn more about Aloe Barbadensis Leaf Extract
Solvent

Propanediol is an all-star ingredient. It softens, hydrates, and smooths the skin. 

It’s often used to:

Propanediol is not likely to cause sensitivity and considered safe to use. It is derived from corn or petroleum with a clear color and no scent.

Learn more about Propanediol
Masking, Preservative, Skin Conditioning

Salicylic Acid (also known as beta hydroxy acid or BHA) is a well-known ingredient for treating skin that struggles with acne and clogged pores. It exfoliates both the skin's surface and deep within the pores to help clear out buildup, control oil, and reduce inflammation.

Unlike AHAs (alpha hydroxy acids), salicylic acid is oil-soluble. This allows it to penetrate into pores which makes it especially effective for treating blackheads and preventing future breakouts.

Salicylic acid is also known for its soothing properties. It has a similar structure to aspirin and can calm inflamed or irritated skin, making it a good option for acne-prone skin that is also sensitive.

Concentrations of 0.5-2% are recognized by the U.S. FDA as an over-the-counter topical acne product.

It can cause irritation and/or dryness if one's skin already has a compromised moisture barrier, so it's best to focus on repairing that before introducing this ingredient into your routine.

While salicylic acid does not increase sun sensitivity, it’s still important to wear sunscreen daily to protect your skin.

If you are looking for the ingredient called BHA or Butylated Hydroxyanisole, click here.

Learn more about Salicylic Acid
Skin Conditioning, Solvent

1,2-Hexanediol is a synthetic liquid and another multi-functional powerhouse. 

It is a:

  • Humectant, drawing moisture into the skin
  • Emollient, helping to soften skin
  • Solvent, dispersing and stabilizing formulas
  • Preservative booster, enhancing the antimicrobial activity of other preservatives 
Buffering, Masking

Sodium Citrate is the sodium salts of citric acid. In skincare, it is used to alter pH levels and acts as a preservative.

Its main functions are to maintain the pH of a product and neutralize metal ions.

The acidity of our skin is maintained by our glands and skin biome; normal pH level of skin is slightly acidic (~4.75-5.5).

Being slightly acidic allows our skin to create an "acid mantle". This acid mantle is a thin barrier that protects our skin from bacteria and contaminants.

Learn more about Sodium Citrate
Emulsifying, Surfactant

Polysorbate 20 is a gentle, water-soluble emulsifier and mild surfactant. It stops oil and water from separating to keep your formulas blended and stable.

It also acts as a mild penetration enhancer by helping active ingredients absorb slightly better.

The common safety discussion around this ingredient involves a manufacturing byproduct called 1,4-dioxane.

Trace amounts can form during production but the EU's Scientific Committee on Consumer Safety has concluded that levels at/below 10 ppm in finished products are safe (commercial products consistently fall within acceptable margins).

True allergic reactions are uncommon and the CIR Expert Panel has confirmed this ingredient to be safe as used in cosmetics.

Because it is derived from lauric acid, it may not be fungal acne safe.

Learn more about Polysorbate 20
Smoothing

Niacinamide is a multitasking form of vitamin B3 that strengthens the skin barrier, reduces pores and dark spots, regulates oil, and improves signs of aging.

And the best part? It's gentle and well-tolerated by most skin types, including sensitive and reactive skin.

You might have heard of "niacin flush", or the reddening of skin that causes itchiness. Niacinamide has not been found to cause this.

In very rare cases, some individuals may not be able to tolerate niacinamide at all or experience an allergic reaction to it.

If you are experiencing flaking, irritation, and dryness with this ingredient, be sure to double check all your products as this ingredient can be found in all categories of skincare.

When incorporating niacinamide into your routine, look out for concentration amounts. Typically, 5% niacinamide provides benefits such as fading dark spots. However, if you have sensitive skin, it is better to begin with a smaller concentration.

When you apply niacinamide to your skin, your body converts it into nicotinamide adenine dinucleotide (NAD). NAD is an essential coenzyme that is already found in your cells as "fuel" and powers countless biological processes.

In your skin, NAD helps repair cell damage, produce new healthy cells, support collagen production, strengthen the skin barrier, and fight environmental stressors (like UV and pollution).

Our natural NAD levels start to decline with age, leading to slower skin repair, visible aging, and a weaker skin barrier. By providing your skin niacinamide, you're recharging your skin's NAD levels. This leads to stronger, healthier, and younger looking skin.

Another name for vitamin B3 is nicotinamide. This vitamin is water-soluble and our bodies don't store it. We obtain Vitamin B3 from either food or skincare. Meat, fish, wheat, yeast, and leafy greens contain vitamin B3.

The type of niacinamide used in skincare is synthetically created.

Learn more about Niacinamide
Masking, Tonic

Rosa Damascena Extract comes from the Damask rose.

The Damask Roses' petals have been found to help sooth skin. The petals also contain antioxidant compounds.

Rosa Damascena Extract is a tonic. Tonics are used to remove soap residues. They also help moisturize the skin.

Learn more about Rosa Damascena Extract
Cleansing, Masking, Refreshing

Lavandula Angustifolia Flower Extract comes from the lavender plant.

Many components of lavender flowers are antioxidants, such as ferulic acid, caffeic acid, and several flavonoids.

Traditional Iranian folk medicine uses Lavender extract to help treat inflammation.

Lavender extract may have a scent.

It contains linalool, a known allergen. However, lavender extract contains less linalool than lavender essential oil.

Learn more about Lavandula Angustifolia Flower Extract
Antimicrobial, Antioxidant, Astringent

Camellia Sinensis Leaf Extract (tea extract) is one of the most well-researched plant extracts in skincare with an impressive resume.

Black tea, green tea, and oolong tea are all harvested from the Camellia Sinensis plant.

Studies show green tea extract and its catechins (like epigallocatechin gallate (EGCG)) help your skin cells product energy more efficiently and reducing the number of free-radicals that can damage your skin from the inside.

In lab-grown skin models, this translated to younger, healthier, and stronger skin.

There's also good sun protection data; researchers saw less DNA damage and redness on human skin when green tea was applied before UVB exposure. And the more they applied, the better the protection.

Needless to say, this ingredient shouldn't replace your sunscreen. But it is a great supportive ingredient that you can already find in many sunscreens and antioxidant serums.

A 2009 study found a 2% green tea lotion was effective for mild-to-moderate acne thanks to its anti-inflammatory and mild antimicrobial activity.

The quality of the extract matters a lot here:

Good extracts contain 50-90% catechins while lower quality ones are mostly there for marketing. We recommend reaching out to the brand if you have questions about the quality or source of their ingredients.

Human Repeated Insult Patch Testing showed no irritation or sensitization at use concentrations (0.86% in leave-on products and up to 30% as leaf water).

Learn more about Camellia Sinensis Leaf Extract

Lemon balm is a mint-family herb with skin conditioning properties. It contains components such as rosmarinic acid, caffeic acid, geraniol, citronellal, and ursolic acid.

Skin Conditioning

Artemisia Vulgaris Extract is more commonly known as the common mugwort. It has strong antioxidant properties and helps soothe irritation.

Antioxidants protect skin from damage and the signs of aging.

This plant contains the compounds saponins, glycosides, flavanoids, protein, triterpenoids.

The common wugwort has been used in traditional Indian, Chinese, and European medicines to treat gastrointestinal diseases.

Learn more about Artemisia Vulgaris Extract
Emulsion Stabilising, Stabilising

Hydroxyethylcellulose is used to improve the texture of products. It is created from a chemical reaction involving ethylene oxide and alkali-cellulose. Cellulose is a sugar found in plant cell walls and help give plants structure.

This ingredient helps stabilize products by preventing ingredients from separating. It can also help thicken the texture of a product.

This ingredient can also be found in pill medicines to help our bodies digest other ingredients.

Learn more about Hydroxyethylcellulose

Reviews

3.4 (current formula)

Average rating of all formulations of this product: 3.4

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Where it's from

Cos De BAHA is a Korean brand

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· Updated July 22, 2025