What Is Oleth-35?
Oleth-35 is a synthetic ingredient made by attaching about 35 units of ethylene oxide to oleyl alcohol, a fatty alcohol that can be sourced from plant oils such as olive or palm. This process, called ethoxylation, turns the oil-like raw material into a water-loving surfactant that can mix oil and water with ease. Chemists started using oleyl-derived ethoxylates in the mid-20th century when the cosmetics industry needed gentler alternatives to harsh soaps. Over time Oleth-35 became popular because its balance of oil and water affinity works well in modern, mild formulations.
The ingredient is produced in controlled reactors where oleyl alcohol and ethylene oxide react under heat and pressure. The resulting liquid is then purified and standardized so each batch delivers roughly the same 35-unit average chain length, giving formulators predictable performance.
You will most often see Oleth-35 in face cleansers, micellar waters, shampoos, conditioners, body washes, makeup removers, exfoliating masks and lightweight moisturizers that need to feel non-greasy yet still rinse clean.
Oleth-35’s Cosmetic Benefits/Uses
Oleth-35 serves a couple of key roles that help products look, feel and perform better
- Cleansing: As a non-ionic surfactant it lowers the surface tension between water and oils lifting away dirt, excess sebum and makeup without leaving a tight after-feel. This makes it ideal for gentle daily cleansers and micellar products.
- Emulsifying: It helps blend oil and water into a stable, uniform mixture so lotions stay creamy and clear gels do not separate. This stability allows brands to include both nourishing oils and refreshing water-based actives in one formula.
Who Can Use Oleth-35
Oleth-35 is generally well tolerated by normal, oily or combination skin because it cleanses without leaving a heavy film. Most dry or sensitive skin can also use it when it is blended into a gentle formula, although very reactive or barrier-impaired skin might prefer surfactants specifically labeled ultra mild since any ethoxylated ingredient can occasionally trigger irritation.
The ingredient is synthetically produced from oleyl alcohol that is usually sourced from plant oils, so it is suitable for vegans and vegetarians as long as the finished product does not include animal-derived additives elsewhere in the formula.
Current safety data suggest Oleth-35 poses minimal risk to people who are pregnant or breastfeeding because it stays on the surface of the skin and is not expected to penetrate in meaningful amounts. This is not medical advice and anyone who is pregnant or nursing should still clear every skincare product with a healthcare provider first to be safe.
Oleth-35 does not cause photosensitivity, meaning it will not make skin more prone to sunburn. It is also compatible with most other common cosmetic ingredients, including vitamin C, niacinamide and retinoids.
Potential Side Effects/Adverse Reactions
Reactions to topical Oleth-35 can vary from person to person. The following is a list of potential side effects that could occur, but they are unlikely for the average user when the ingredient has been formulated correctly.
- Mild skin irritation transient redness, itching or a stinging sensation, most often on already sensitized skin
- Contact dermatitis rare allergic response that can result in rash or swelling
- Eye irritation possible watering or stinging if a cleanser or shampoo accidentally gets into the eyes
- Dryness overuse in high-foaming formulas may strip natural oils leaving skin or hair feeling tight or brittle
If you notice any of the above reactions stop using the product and consult a medical professional.
Comedogenic Rating
Rating: 1/5
Oleth-35 is a large non-ionic surfactant that stays mostly on the surface and is usually rinsed away, so it has very little chance of settling into pores and causing blockages. Although it is derived from a fatty alcohol, the high degree of ethoxylation makes the molecule far more water friendly than oil like, which further reduces pore-clogging potential. In most cleanser and lotion formulas it is used at low to moderate levels and is typically part of a blend rather than the main emollient, keeping its comedogenic risk low.
Because of this low score it is considered suitable for people who are prone to acne or frequent breakouts.
Comedogenicity can still rise slightly if the ingredient sits on the skin for long periods in rich leave-on products, but that scenario is uncommon since Oleth-35 is primarily used in rinse-off or lightweight systems.
Summary
Oleth-35 is a multifunctional ingredient that acts as a gentle cleanser and an effective emulsifier. By lowering surface tension it helps water lift away dirt, makeup and excess oil while its oil-in-water balancing ability keeps creams and gels from separating.
It is not a headline star like hyaluronic acid or niacinamide yet formulators reach for it often because it delivers reliable performance without a greasy feel. You will find it quietly doing its job in everyday face washes, micellar waters and lightweight lotions across many brands.
Current safety assessments show Oleth-35 is generally low risk with only occasional mild irritation in sensitive users. As with any new cosmetic ingredient it is wise to test a small area first to be sure your skin agrees with it.