Ingredient review
Ethyl Ester of Hydrolyzed Keratin
INCI: ETHYL ESTER OF HYDROLYZED KERATIN
A gentle, modified keratin protein that forms a protective film on hair and skin to improve strength, moisture retention, and manageability.
In plain English
This ingredient is a modified version of keratin, the protein that naturally makes up your hair, skin, and nails. By adding an ethyl ester group, it becomes more soluble and can better penetrate or adhere to hair and skin surfaces. It works by forming a thin, flexible film that helps lock in moisture, smooth the cuticle, and temporarily reinforce the hair shaft, making hair feel stronger, shinier, and less prone to breakage. On skin, it provides a light, protective layer that can help reduce water loss and improve softness.
Review score
Safety, usefulness, and evidence
Potentially useful with some tradeoffs
The evidence base is useful, but some claims depend heavily on the formula.
Risk flags are low for most users, though the finished product can still irritate.
- Source
- semi synthetic
- Evidence
- moderate
- Irritation
- low
- Clogging risk
- low
Quick decision guide
Useful, but context matters
Ethyl Ester of Hydrolyzed Keratin is generally a lower-concern ingredient when the full formula suits your skin.
Plain-English read
Treat this as a practical screening step before you compare products that contain this ingredient.
- Step 1Start with the score, then check the irritation and clogging risk before judging Ethyl Ester of Hydrolyzed Keratin.
- Step 2Use the "Best for" and "Use caution if" sections to match the ingredient to your skin, not just to a marketing claim.
- Step 3If a product stings, breaks you out, or worsens irritation, judge the finished formula and stop using it even if the ingredient scores well.
Score terms in plain English
Irritation risk
lowLess likely to sting, burn, or bother most users, though sensitive skin can still react.
Clogging risk
lowLess likely to feel heavy or contribute to clogged pores for most skin types.
Evidence level
moderateThere is useful support, but formula details and claim strength still matter.
What it is
A semi-synthetic derivative of keratin, created by hydrolyzing natural keratin (often from wool or feathers) and then esterifying it with ethanol. This process makes the protein more lipophilic (oil-loving) and better able to bind to hair and skin.
How it works
When applied, the ethyl ester of hydrolyzed keratin deposits onto the hair or skin surface. Its modified structure allows it to form a thin, flexible film that fills in gaps in the cuticle or stratum corneum. This film helps reduce moisture loss, smooth roughness, and provide temporary strengthening by cross-linking with the natural keratin structure. On hair, it can reduce frizz and improve manageability; on skin, it can enhance barrier function and leave a soft, non-greasy feel.
Pros
Temporary hair strengthening
Forms a protective film that can help reduce breakage and improve hair resilience until the next wash.
Lightweight moisture barrier
Provides a non-greasy film on skin and hair that helps lock in moisture without feeling heavy or sticky.
Cons and cautions
Temporary effect
The strengthening and smoothing benefits are not permanent and are removed with shampooing, requiring frequent reapplication.
Potential buildup
On fine or low-porosity hair, repeated use can lead to protein buildup, making hair feel stiff or dry.
Best for
- People with damaged, brittle, or over-processed hair looking for temporary strengthening
- Those with dry or dehydrated skin wanting a lightweight, film-forming moisturizer
Use caution if
- Individuals with very fine or low-porosity hair who may experience buildup or stiffness
Usage tips
Safety summary
Ethyl ester of hydrolyzed keratin is considered safe for topical use in cosmetics at typical concentrations. It has a low irritation and comedogenic risk. However, individuals with known allergies to keratin or animal proteins should patch test first.
Research notes
Research on hydrolyzed keratin and its derivatives shows they can improve hair strength, reduce moisture loss, and enhance hair manageability. Studies on the ethyl ester specifically are limited, but the mechanism is well understood based on related protein derivatives. Evidence is moderate and primarily from in vitro and human panel studies.
Common label clues
- Typical concentration
- 0.1% to 2%
- Regulatory status
- Generally recognized as safe for use in cosmetics in the US and EU when used as directed. No specific restrictions beyond standard cosmetic ingredient regulations.
- Common uses
- Shampoos, Conditioners, Hair masks, Leave-in treatments, Serums, Moisturizers
- Environmental note
- Keratin is typically sourced from animal by-products (wool, feathers), making it a by-product of the meat industry. The esterification process uses ethanol, which is generally considered low-impact.
Good to know
- This ingredient is often listed near the middle or end of an ingredient list, indicating a lower concentration.
- It is compatible with most other hair and skin ingredients, including oils, silicones, and humectants.
Common questions
What is Ethyl Ester of Hydrolyzed Keratin in beauty products?
This ingredient is a modified version of keratin, the protein that naturally makes up your hair, skin, and nails. By adding an ethyl ester group, it becomes more soluble and can better penetrate or adhere to hair and skin surfaces. It works by forming a thin, flexible film that helps lock in moisture, smooth the cuticle, and temporarily reinforce the hair shaft, making hair feel stronger, shinier, and less prone to breakage. On skin, it provides a light, protective layer that can help reduce water loss and improve softness.
What does Ethyl Ester of Hydrolyzed Keratin do in a beauty product?
When applied, the ethyl ester of hydrolyzed keratin deposits onto the hair or skin surface. Its modified structure allows it to form a thin, flexible film that fills in gaps in the cuticle or stratum corneum. This film helps reduce moisture loss, smooth roughness, and provide temporary strengthening by cross-linking with the natural keratin structure. On hair, it can reduce frizz and improve manageability; on skin, it can enhance barrier function and leave a soft, non-greasy feel.
Is Ethyl Ester of Hydrolyzed Keratin safe for most people?
Ethyl ester of hydrolyzed keratin is considered safe for topical use in cosmetics at typical concentrations. It has a low irritation and comedogenic risk. However, individuals with known allergies to keratin or animal proteins should patch test first.
Who should be careful with Ethyl Ester of Hydrolyzed Keratin?
Individuals with very fine or low-porosity hair who may experience buildup or stiffness
Research sources
Ingredient reviews are educational and are not medical advice. Patch test new products and ask a licensed clinician about persistent irritation, allergies, pregnancy-specific questions, or diagnosed skin conditions.