What Is Isostearoyl Hydrolyzed Keratin?
Isostearoyl Hydrolyzed Keratin is a hybrid ingredient that pairs tiny keratin peptides with isostearic acid, a fatty acid most often sourced from plant oils such as rapeseed or coconut. The keratin side comes from wool or other keratin-rich materials that are gently broken down, or hydrolyzed, into smaller pieces so they can sink into hair and skin. Chemists then bond these peptides to isostearic acid chloride, creating a molecule that is both water friendly and oil friendly. This dual nature helps the ingredient blend easily into modern cosmetic formulas.
Keratin itself has been used in hair care since the mid-20th century, but early versions were hard to mix into products. By attaching a fatty acid, brands gained a more stable, more compatible form that took off in the 2000s. Today Isostearoyl Hydrolyzed Keratin appears in many rinse-off and leave-on items, including shampoos, conditioners, hair masks, blow-dry creams, skin moisturizers, body washes and anti-aging serums.
Isostearoyl Hydrolyzed Keratin’s Cosmetic Benefits/Uses
Because this ingredient bridges protein repair with a touch of fatty conditioning, it offers several perks in a formula:
- Cleansing: Its mild surfactant action helps lift away excess oil and buildup without stripping, giving a gentle cleanse in shampoos and body washes.
- Hair conditioning: The keratin peptides can patch tiny cracks along the hair shaft while the fatty portion smooths the cuticle, leading to softer, glossier strands and easier detangling.
- Skin conditioning: On skin it forms a light film that holds moisture, supports a supple feel and may improve the look of rough or flaky spots.
Who Can Use Isostearoyl Hydrolyzed Keratin
This ingredient is generally considered suitable for all skin and hair types, from dry to oily to combination. Its lightweight film-forming nature means it rarely feels heavy or greasy, making it comfortable even for acne-prone or sensitive skin. People with a known wool or lanolin allergy, however, should proceed with caution because the keratin portion is typically sourced from wool and could trigger a reaction.
Because that keratin comes from an animal source, Isostearoyl Hydrolyzed Keratin is not a vegan ingredient. Strict vegetarians may also choose to avoid it for the same reason. Those following a plant-only lifestyle can look for products that feature hydrolyzed plant proteins instead.
No research suggests that topical use poses unique risks to women who are pregnant or breastfeeding. Still this is not medical advice and anyone expecting or nursing should ask a healthcare professional before adding new products to their routine, just to be safe.
The molecule does not make skin more sensitive to sunlight so there is no special need for extra sun precautions beyond everyday SPF habits.
Potential Side Effects/Adverse Reactions
Reactions to Isostearoyl Hydrolyzed Keratin vary from person to person. The points below outline potential side effects yet most people will not experience them when using well-formulated products.
- Allergic contact dermatitis – itching, redness or rash for individuals allergic to wool proteins or other formulation components
- Mild skin or scalp irritation – stinging or dryness if the overall formula is too strong or used too frequently
- Acne flare-ups – rare clogged pores in very oil-rich leave-on products on acne-prone areas
- Build-up on hair – dullness or limp strands if heavy conditioners containing the ingredient are not rinsed thoroughly
If any of these effects occur stop use and consult a qualified healthcare provider or dermatologist
Comedogenic Rating
Rating: 1 / 5
Isostearoyl Hydrolyzed Keratin is mostly made of small keratin peptides that do not clog pores. The isostearic fatty acid portion is lightweight and highly branched so it spreads easily rather than settling into follicles. Formulas tend to use it at low to moderate levels which keeps the overall risk of pore blockage minimal. For these reasons it earns a low comedogenic score of 1.
That rating means the ingredient is generally suitable for people who are prone to acne or breakouts, especially when used in rinse-off or well-balanced leave-on products.
As with any multifunctional ingredient the final product matters: if a cream is very rich or layered with other heavy oils it could still feel occlusive even if this single component is low risk.
Summary
Isostearoyl Hydrolyzed Keratin cleanses, conditions hair and conditions skin. The keratin peptides slip into tiny cracks on hair or the skin surface, reinforcing weak spots and boosting smoothness. The attached isostearic acid adds mild surfactant action for gentle cleansing and leaves behind a soft, flexible film that locks in moisture and shine.
While not as common as classic hydrolyzed keratin or plain fatty acids this hybrid is popping up more often in modern shampoos, conditioners, styling creams and a handful of skin treatments because formulators like its balanced blend of protein repair and light conditioning.
Current data shows it is low-risk for irritation or clogged pores for most users. Still skin is personal so it is smart to patch test any new product that features this ingredient before making it a staple in your routine.