What Is Sesquiethoxytriethanolamine?
Sesquiethoxytriethanolamine is a synthetic compound created by reacting ammonia with ethylene oxide, which results in a blend made mostly of triethanolamine together with hydroxyethoxyethyl diethanolamine. This balanced mix gives it a mild alkaline nature, making the ingredient useful for keeping formulas at the right pH.
The cosmetic industry first turned to derivatives of triethanolamine in the mid-1900s when chemists looked for gentler ways to stabilize creams and lotions. As demand grew for multi-tasking ingredients that save space on an ingredient list, sesquiethoxytriethanolamine found a niche thanks to its ability to buffer, cleanse and support smooth textures all at once.
Manufacturing starts with carefully controlled batches where ammonia and ethylene oxide react in closed tanks. The resulting liquid is purified to remove excess reactants, then tested for consistency and safety before shipment to formulators.
You will most often spot sesquiethoxytriethanolamine in facial cleansers, lightweight moisturizers, clay or gel masks, leave-on anti-aging serums, hair dyes, shaving creams and some deodorant sticks. Formulators appreciate that a small amount can fine-tune pH while also helping oil and water stay mixed, reducing the need for multiple separate additives.
Sesquiethoxytriethanolamine’s Cosmetic Benefits/Uses
When included at the right level this ingredient supports both the performance and feel of a product in several ways:
- Buffering: Keeps the formula’s pH steady so that active ingredients work as intended and skin feels comfortable rather than irritated
- Emulsion Stabilising: Prevents creams and lotions from separating during storage which means a longer shelf life and a uniform texture every time you use the product
- Cleansing: Helps loosen oil and grime allowing them to rinse away more easily so cleansers feel effective yet gentle
- Emulsifying: Allows water and oil phases to blend smoothly producing lightweight creams that spread evenly without leaving a greasy film
Who Can Use Sesquiethoxytriethanolamine
This multifunctional ingredient is generally well tolerated by most skin types including normal, oily, combination and even many sensitive skins thanks to its low use levels and mild cleansing action. Very reactive or compromised skin might want to proceed with care because its slightly alkaline nature can, in rare cases, disrupt an already fragile skin barrier.
Sesquiethoxytriethanolamine is synthetically produced with no animal-derived components so it is suitable for vegans and vegetarians. As always, cruelty-free status will depend on the final brand’s testing policies rather than the ingredient itself.
No published research flags special concerns for women who are pregnant or breastfeeding when the ingredient is used in rinse-off or leave-on cosmetics at typical concentrations. That said this is not medical advice and anyone who is pregnant or nursing should run any skincare product past a qualified healthcare provider to be on the safe side.
The ingredient does not induce photosensitivity so there is no need for extra sun precautions beyond the daily SPF dermatologists already recommend. It also plays well with most common actives such as vitamin C and niacinamide because its buffering action helps keep overall pH in a comfortable range.
Potential Side Effects/Adverse Reactions
Individual responses to topical sesquiethoxytriethanolamine can differ. The points below list potential effects that have been reported in the literature or by formulators, though they are unlikely to occur for the average user when the ingredient is used correctly in a finished product.
- Temporary stinging or tingling on very sensitive or freshly exfoliated skin
- Mild redness or irritation if the formula’s pH is not properly adjusted
- Allergic contact dermatitis in individuals with an existing sensitivity to ethanolamine compounds
- Eye irritation if a product accidentally gets into the eyes
- Dryness or tightness when used at higher concentrations or in multiple products within the same routine
- Formation of potentially harmful nitrosamines if combined with strong nitrosating agents, something reputable formulators actively avoid
If any of these effects are noticed discontinue use and consult a healthcare professional if symptoms persist or worsen.
Comedogenic Rating
Rating: 1/5
Sesquiethoxytriethanolamine is highly water soluble and used at very low levels, so it does not sit on the skin or clog pores. Its primary role is to balance pH and help oil and water mix, not to create a heavy film that could trap sebum and debris. For these reasons formulators consider it to have a very low comedogenic potential.
Acne prone users can typically use products containing this ingredient without extra worry, provided the overall formula suits their skin.
Published comedogenicity testing on this specific compound is limited, but data on its close relative triethanolamine supports the low rating.
Summary
Sesquiethoxytriethanolamine acts as a pH buffer, mild cleanser, emulsifier and emulsion stabiliser. Its alkaline nature neutralises excess acids to keep a comfortable pH, while its mixed water loving and oil loving structure lets it bridge and stabilise oil in water systems so creams stay smooth and light. It also lowers surface tension to help rinse away grime.
The ingredient is a quiet workhorse rather than a headline star. It shows up in a modest selection of cleansers, lotions and hair products where formulators need a space saving multitasker, but it is not as widely used as better known bases like triethanolamine.
Regulatory bodies deem it safe in rinse off and leave on products at the concentrations normally used, with irritation or allergy remaining uncommon. As with any new cosmetic it is smart to patch test a product containing sesquiethoxytriethanolamine before full use to make sure your skin agrees with it.