Ingredient review
Polylysine HBr
INCI: POLYLYSINE HBR
A gentle, fermentation-derived preservative booster that helps keep products fresh without harsh chemicals.
In plain English
Polylysine HBr is a natural preservative booster made from fermented bacteria. It helps prevent the growth of bacteria, yeast, and mold in your skincare products, so they stay safe to use longer. Unlike some traditional preservatives, it is very gentle on skin and unlikely to cause irritation. Think of it as a friendly bodyguard for your moisturizer or serum.
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
- biotech
- Evidence
- moderate
- Irritation
- low
- Clogging risk
- low
Quick decision guide
Useful, but context matters
Polylysine HBr 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 Polylysine HBr.
- 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
Polylysine HBr is a salt form of polylysine, a natural antimicrobial peptide produced by fermentation of the bacterium Streptomyces albulus. It is used in cosmetics as a broad-spectrum preservative booster, often combined with other preservatives to reduce their overall concentration.
How it works
Polylysine HBr works by disrupting the cell membranes of microorganisms like bacteria and fungi, causing them to break down and die. This action helps protect your skincare products from contamination, extending their shelf life without relying on high levels of traditional preservatives.
Pros
Gentle on skin
Polylysine HBr has a very low irritation risk, making it suitable for sensitive skin types and baby products.
Natural origin
Derived from fermentation, it appeals to consumers seeking more naturally sourced preservative options.
Cons and cautions
Not a standalone preservative
It is typically used as a booster alongside other preservatives, not as a complete preservative system on its own.
Limited efficacy range
Its antimicrobial activity can be reduced in formulas with extreme pH levels, requiring careful formulation.
Best for
- Anyone looking for a gentler preservative system
- People with sensitive or reactive skin
- Those who prefer fermentation-derived ingredients
Use caution if
- Individuals with a known allergy to polylysine (very rare)
Usage tips
Safety summary
Polylysine HBr is considered safe for use in cosmetics at typical concentrations. It has a low irritation and sensitization potential, and no significant safety concerns have been identified in regulatory reviews.
Research notes
Research supports its antimicrobial efficacy against a range of bacteria and fungi. Studies indicate it is well-tolerated on skin and does not cause significant irritation or allergic reactions.
Common label clues
- Typical concentration
- 0.1% to 1%
- Regulatory status
- Approved for use in cosmetics in the EU, US, and many other countries. It is not a restricted ingredient but is subject to general cosmetic safety regulations.
- Common uses
- Preservative systems, Leave-on products, Rinse-off products
- Environmental note
- Produced via fermentation, which is generally considered more sustainable than chemical synthesis. It is biodegradable and has low environmental toxicity.
Good to know
- Polylysine HBr is often listed as 'Polylysine' or 'Epsilon-polylysine' on ingredient labels.
- It is approved for use in cosmetics in many regions, including the EU and US.
Common questions
What is Polylysine HBr in beauty products?
Polylysine HBr is a natural preservative booster made from fermented bacteria. It helps prevent the growth of bacteria, yeast, and mold in your skincare products, so they stay safe to use longer. Unlike some traditional preservatives, it is very gentle on skin and unlikely to cause irritation. Think of it as a friendly bodyguard for your moisturizer or serum.
What does Polylysine HBr do in a beauty product?
Polylysine HBr works by disrupting the cell membranes of microorganisms like bacteria and fungi, causing them to break down and die. This action helps protect your skincare products from contamination, extending their shelf life without relying on high levels of traditional preservatives.
Is Polylysine HBr safe for most people?
Polylysine HBr is considered safe for use in cosmetics at typical concentrations. It has a low irritation and sensitization potential, and no significant safety concerns have been identified in regulatory reviews.
Who should be careful with Polylysine HBr?
Individuals with a known allergy to polylysine (very 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.