Peg-5 Castor Oil: 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: July 1, 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 Peg-5 Castor Oil?

Peg-5 Castor Oil starts with regular castor oil, the thick vegetable oil pressed from the seeds of the Ricinus communis plant. Chemists react this oil with a small amount of ethylene oxide, on average five units per castor oil molecule, to create a lighter ingredient that mixes easily with water. This process is called ethoxylation and it turns heavy, water-repelling castor oil into a water-friendly liquid that can act as a gentle cleanser and helper for mixing oil with water.

Castor oil itself has been used for skin and hair care since ancient times. In the mid-20th century formulators began tweaking natural oils with ethylene oxide to make modern surfactants. Peg-5 Castor Oil was one of the results, valued for the way it lifts away dirt without stripping the skin.

You will most often see Peg-5 Castor Oil in facial cleansers, micellar waters, makeup removers, exfoliating masks, lightweight moisturizers, scalp scrubs and conditioning hair serums. It is usually included at low levels to keep formulas stable and silky.

Peg-5 Castor Oil’s Cosmetic Benefits/Uses

This ingredient offers two main functions that improve both the feel and performance of beauty products.

  • Cleansing – Works as a mild surfactant that grabs onto oil, sweat and makeup, then rinses them away with water. Because it is derived from a natural oil it tends to be less drying than stronger detergents, making it suitable for sensitive or mature skin.
  • Emulsifying – Helps oil and water stay blended so a lotion, cream or serum remains smooth from the first pump to the last. A stable emulsion spreads evenly, feels pleasant on the skin and delivers active ingredients more consistently.

Who Can Use Peg-5 Castor Oil

Peg-5 Castor Oil suits most skin types including normal, dry, combination and oily because it cleanses gently without leaving a heavy film. Those with very sensitive or allergy-prone skin can usually tolerate it as it is milder than many synthetic detergents, however anyone with a known castor seed allergy should avoid it.

The ingredient is plant derived and produced without animal by-products so it is considered suitable for vegans and vegetarians.

No data suggest particular risks for women who are pregnant or breastfeeding when Peg-5 Castor Oil is applied topically at the low levels used in cosmetics. This is not medical advice, and expecting or nursing mothers should still check any skincare product with their doctor to be safe.

Peg-5 Castor Oil does not increase photosensitivity so it will not make skin more prone to sunburn. It also has no known issues with hair color treatments, self-tanners or other common beauty steps.

Potential Side Effects/Adverse Reactions

Reactions to topical Peg-5 Castor Oil vary from person to person. The following are potential side effects, but most users will not experience them when the ingredient is formulated and used correctly.

  • Skin irritation such as redness or stinging in very sensitive individuals
  • Contact dermatitis in people allergic to castor oil or polyethylene glycols
  • Temporary dryness or tightness if used in a high-foaming cleanser without added moisturizers
  • Mild eye irritation if the product accidentally gets into the eyes
  • Enhanced penetration of other actives, which could amplify their own irritating effects

If a negative reaction occurs stop using the product and seek medical advice if symptoms persist or worsen.

Comedogenic Rating

Comedogenic rating: 1 out of 5. Peg-5 Castor Oil is partly water loving thanks to its ethoxylated groups so it rinses off instead of sitting in pores. The molecule is also fairly large which further lowers its tendency to block follicles.

Most acne prone users can use products containing this ingredient without seeing extra breakouts. Any pimples that do appear are more likely linked to heavier oils or waxes elsewhere in the formula.

Its ability to help other oils wash away cleanly makes it a handy addition to cleansing balms or micellar waters designed for congested skin.

Summary

Peg-5 Castor Oil works as a mild cleanser and an emulsifier. The castor oil part grabs makeup dirt and sebum while its polyethylene glycol chains let that mix lift away with water and keep oil and water blended inside the bottle.

It is a solid team player rather than a headline act so you will spot it here and there in gentle cleansers makeup removers and light lotions but not in every product on the shelf.

The ingredient is considered low risk and has a long track record of safe use in cosmetics. Still it is smart to patch test any new product containing Peg-5 Castor Oil to be sure your skin stays happy.

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