Ingredient review
Polyhydroxybutyrate
INCI: POLYHYDROXYBUTYRATE
A gentle, biodegradable film-former that helps lock in moisture and may support the skin barrier.
In plain English
Polyhydroxybutyrate is a natural polymer made by bacteria, similar to the building blocks of some plant waxes. In skincare, it forms a thin, breathable film on your skin that helps prevent water loss and keeps your skin feeling soft and hydrated. Think of it like a light, invisible shield that holds moisture in without feeling heavy or sticky.
Review score
Safety, usefulness, and evidence
Potentially useful with some tradeoffs
The evidence base is still emerging, so marketing claims deserve extra caution.
Risk flags are low for most users, though the finished product can still irritate.
- Source
- biotech
- Evidence
- emerging
- Irritation
- low
- Clogging risk
- low
Quick decision guide
Useful, but context matters
Polyhydroxybutyrate 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 Polyhydroxybutyrate.
- 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
emergingThe ingredient may be promising, but claims should be treated more cautiously.
What it is
Polyhydroxybutyrate (PHB) is a polyester produced by bacterial fermentation. It is a type of polyhydroxyalkanoate (PHA), a family of biodegradable plastics. In cosmetics, it is used as a film-forming agent and moisturizer.
How it works
When applied to the skin, PHB forms a thin, flexible film that reduces transepidermal water loss (TEWL), meaning less water evaporates from your skin. This helps maintain hydration and supports the skin barrier function. It also gives a smooth, silky feel to products.
Pros
Eco-friendly origin
PHB is produced by bacteria and is fully biodegradable, making it a more sustainable choice compared to some synthetic film-formers.
Gentle on skin
It has a low irritation and comedogenic risk, so it is suitable for sensitive and acne-prone skin types.
Cons and cautions
Limited research
Compared to well-studied ingredients like hyaluronic acid, there is less published research on PHB's specific benefits for skin health.
Not a deep humectant
PHB primarily works by forming a surface film to prevent water loss, rather than drawing water into the skin like glycerin or hyaluronic acid.
Best for
- People with dry or dehydrated skin looking for a gentle moisture-locking ingredient
- Those interested in sustainable, biotech-derived skincare ingredients
Use caution if
- Individuals with known allergies to bacterial fermentation products (rare)
Usage tips
Safety summary
Polyhydroxybutyrate is considered safe for use in cosmetics. It has low irritation and comedogenic potential, and no significant safety concerns have been reported in the available literature.
Research notes
Research on PHB in cosmetics is still emerging. Most evidence comes from material science and biocompatibility studies, with limited direct clinical trials on skin benefits. However, its film-forming and moisture-retention properties are well-documented in related fields.
Common label clues
- Typical concentration
- 0.5% to 5%
- Regulatory status
- Approved for use in cosmetics in the EU, US, and other major markets. No specific restrictions known at typical use levels.
- Common uses
- Moisturizers, Serums, Masks, Sunscreens
- Environmental note
- PHB is produced through bacterial fermentation and is biodegradable, making it a more environmentally friendly alternative to some petroleum-based film-formers.
Good to know
- PHB is often used in 'green' or sustainable beauty products due to its biodegradable nature.
- It is not a common ingredient yet, so you may find it listed in more niche or eco-conscious brands.
Common questions
What is Polyhydroxybutyrate in beauty products?
Polyhydroxybutyrate is a natural polymer made by bacteria, similar to the building blocks of some plant waxes. In skincare, it forms a thin, breathable film on your skin that helps prevent water loss and keeps your skin feeling soft and hydrated. Think of it like a light, invisible shield that holds moisture in without feeling heavy or sticky.
What does Polyhydroxybutyrate do in a beauty product?
When applied to the skin, PHB forms a thin, flexible film that reduces transepidermal water loss (TEWL), meaning less water evaporates from your skin. This helps maintain hydration and supports the skin barrier function. It also gives a smooth, silky feel to products.
Is Polyhydroxybutyrate safe for most people?
Polyhydroxybutyrate is considered safe for use in cosmetics. It has low irritation and comedogenic potential, and no significant safety concerns have been reported in the available literature.
Who should be careful with Polyhydroxybutyrate?
Individuals with known allergies to bacterial fermentation products (rare)
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.