Undeceth-5: What Is It, Cosmetic Uses, Benefits & Side Effects

Curious about this ingredient? In this article we're explaining exactly what it is and why it's used within cosmetic formulations.
Updated on: June 30, 2025
Share:
Inside this article:

We verify all information on this page using publicly available nomenclature standards from The Personal Care Products Council (PCPC), the European Commission's CosIng database and documentation provided directly by ingredient manufacturers. Our analysis is based on technical data from these sources to ensure accuracy and reliability.

What Is Undeceth-5?

Undeceth-5 is a synthetic ingredient made by reacting undecyl alcohol, which is derived from fatty acids found in natural oils, with ethylene oxide. The reaction adds an average of five ethylene oxide units to each molecule, creating a water-loving end and an oil-loving end. This dual nature lets it mix oil and water with ease, a property chemists call surfactancy.

The use of ethoxylated fatty alcohols like Undeceth-5 grew in the mid-20th century when manufacturers searched for milder alternatives to traditional soaps. Its balanced cleansing action and ability to build stable emulsions quickly secured it a place in personal care labs. Today the ingredient is produced in large-scale reactors where temperature, pressure and pH are carefully controlled to ensure consistent chain length and purity.

You will most often spot Undeceth-5 in rinse-off cleansers, micellar waters, makeup removers, facial masks, lightweight lotions and hair conditioners. Formulators value it for its gentle feel and versatility, especially in products designed for sensitive or combination skin.

Undeceth-5’s Cosmetic Benefits/Uses

Formulators choose Undeceth-5 for two main reasons that directly improve how a product works and feels.

  • Cleansing: Its surfactant structure lifts away dirt, oil and makeup without stripping the skin or hair, helping leave a clean yet comfortable finish.
  • Emulsifying: It binds water and oil phases into a smooth, uniform mixture, preventing separation and giving creams, lotions and masks a stable, silky texture.

Who Can Use Undeceth-5

Undeceth-5 is generally suitable for all skin types including oily, combination, normal, dry, sensitive and mature skin. Its mild cleansing action rarely strips moisture, yet people with very dry or compromised skin may prefer formulations where it is paired with richer emollients to offset any potential tightness.

The ingredient is manufactured from synthetic or plant-derived fatty alcohols and contains no animal by-products, making it appropriate for both vegans and vegetarians.

Current safety data show no specific risks for pregnant or breastfeeding women when Undeceth-5 is used topically at the low levels found in cosmetics. This is informational only and not medical advice; anyone who is pregnant or nursing should discuss new skincare products with a qualified health professional.

Undeceth-5 does not increase photosensitivity, so it will not make skin more prone to sunburn. It is also non-comedogenic and rinses away cleanly, which helps keep pores clear.

Potential Side Effects/Adverse Reactions

Responses to topical ingredients vary from person to person. The following list covers potential side effects of Undeceth-5, yet most users experience none of these issues when the ingredient is used at standard cosmetic levels.

  • Mild skin irritation such as redness or stinging, most often in very sensitive individuals
  • Transient eye irritation if a cleanser containing Undeceth-5 gets into the eyes
  • Dryness or tightness when used in high-foaming products without added moisturizers
  • Rare allergic contact dermatitis presenting as itching or small bumps
  • Scalp irritation in some people when used in concentrated hair treatments

If any discomfort, persistent redness or rash occurs stop using the product and seek advice from a healthcare professional or dermatologist.

Comedogenic Rating

Rating: 0 / 5

Undeceth-5 is a small, water-soluble surfactant that does not leave an oily film behind, so it is very unlikely to clog pores. It rinses away completely and is used at low levels, which further reduces any buildup on the skin.

Because of this, Undeceth-5 is generally suitable for acne-prone or breakout-prone skin.

No additional concerns related to comedogenicity have been reported in the scientific or regulatory literature.

Summary

Undeceth-5 acts as a gentle cleanser and a reliable emulsifier. Its molecule has a water-loving end and an oil-loving end, allowing it to lift away grime while helping oil and water blend into stable, smooth formulas.

The ingredient is moderately popular in modern skincare and haircare, especially in micellar waters, mild face washes and lightweight lotions where formulators need cleansing power without harshness.

Current research and regulatory reviews rate Undeceth-5 as safe at the concentrations used in cosmetics. Still, skin can be unpredictable, so it is smart to patch test any new product that contains this ingredient before full use.

Was this article helpful?
More from Glooshi:
ADVERTISEMENT
Get all our top headlines in beauty.
Delivered right to your inbox each week. Zero spam, all goodness, opt-out at anytime.
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Get the latest beauty news, top product recommendations & brand-exclusive discount codes direct to your inbox.
Send good feedback:

All feedback is greatly appreciated, anonymous, and will be used to improve the quality of our articles.

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Send bad feedback:

All feedback is greatly appreciated, anonymous, and will be used to improve the quality of our articles.

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Search