What Is Peg-6 Undecylenate?
Peg-6 Undecylenate is a liquid ingredient made by attaching six units of ethylene oxide to undecylenic acid, a fatty acid that can be derived from castor oil or other plant oils. This process, called ethoxylation, turns the raw acid into a gentle surfactant that mixes well with both water and oil. Chemists first started using ethoxylated fatty acids in the mid-20th century when they were looking for milder cleansers for personal care. Peg-6 Undecylenate found its place in cosmetics because it offered cleansing power without the harshness of traditional soaps.
The ingredient is produced in a controlled reaction where undecylenic acid is combined with ethylene oxide gas under heat and pressure. The result is a clear to pale yellow liquid that blends easily into water-based or oil-based formulas.
You will most often see Peg-6 Undecylenate in facial cleansers, micellar waters, makeup removers, scalp treatments, clarifying masks and lightweight moisturizers that aim to keep skin fresh and balanced.
Peg-6 Undecylenate’s Cosmetic Benefits/Uses
In formulas Peg-6 Undecylenate serves two main roles that improve how a product feels and performs on skin or hair
- Cleansing: Acts as a mild surfactant that lifts away dirt, oil and makeup while keeping the skin barrier comfortable. It creates a soft foam and rinses clean which helps leave skin feeling refreshed not stripped
- Anti-Seborrheic: Helps control excess sebum on skin and scalp. By reducing surface oil it can support a clearer look and make hair feel lighter between washes
Who Can Use Peg-6 Undecylenate
This ingredient is generally suitable for oily, combination and normal skin types because it helps sweep away excess sebum without stripping the surface. Acne-prone skin often benefits too since a cleaner pore environment can support clearer looking skin. Dry or very sensitive complexions can still use it in low amounts though they may prefer formulas paired with extra moisturizers to offset any slight oil-reducing effect.
Peg-6 Undecylenate is usually sourced from castor oil, a plant-based feedstock, and processed with synthetic ethylene oxide, so it is typically free of animal-derived components. That makes it acceptable for most vegan and vegetarian lifestyles, provided the end product has not been tested on animals.
No studies have flagged Peg-6 Undecylenate as a concern for pregnancy or breastfeeding. The molecule stays on the skin’s surface and is not expected to enter the bloodstream in meaningful amounts. This is not medical advice; anyone who is pregnant or nursing should review their skincare routine with a qualified healthcare professional just to be safe.
The ingredient does not increase photosensitivity, so it will not make skin more prone to sunburn. It also plays well with common actives like niacinamide or salicylic acid and does not interfere with makeup wear.
Potential Side Effects/Adverse Reactions
Responses to topical Peg-6 Undecylenate differ from person to person. The points below list potential side effects, yet most users will not experience them when the ingredient is included at typical cosmetic levels and the product is correctly formulated.
- Mild skin irritation such as tingling or redness, especially on very sensitive skin
- Transient dryness or tightness after cleansing if the rest of the formula lacks replenishing ingredients
- Allergic contact dermatitis in individuals already sensitized to ethoxylated fatty acids
- Eye stinging or watering if a cleanser containing the ingredient is not thoroughly rinsed away
If any discomfort or persistent reaction occurs stop using the product and consult a medical professional for guidance.
Comedogenic Rating
Rating: 1/5. Peg-6 Undecylenate is highly water soluble thanks to its six ethylene oxide units, so it rinses off the skin rather than lingering inside pores. Although it originates from a fatty acid, the ethoxylation process strips away most oil-like behavior, making it very unlikely to block follicles. In real-world formulas it is usually present at low levels and paired with additional surfactants that further reduce residue. For these reasons it is considered safe for people prone to acne or breakouts.
Keep in mind that comedogenicity can shift depending on the overall product, concentration and how completely it is rinsed away. Individual skin chemistry also plays a role so experiences can vary.
Summary
Peg-6 Undecylenate is a gentle, plant-derived surfactant that cleanses the skin while helping curb excess oil. It lifts away dirt and makeup without stripping the barrier and its anti-seborrheic edge makes it handy for balancing oily or combination complexions. Usage is moderate rather than widespread because many brands rely on more common surfactants like PEG-7 Glyceryl Cocoate or Polysorbates, yet formulators who need a mild oil-reducing cleanser still reach for it.
Current safety data shows very low irritation potential when used at cosmetic levels and no evidence of long-term harm. As with any new skincare ingredient it is smart to patch test a fresh product first to make sure your skin agrees with the full formula.