Understanding Hurdle Technology in Cosmetic Preservation

How Can We Reduce Preservative Load Without Sacrificing Safety?

Preserving cosmetic products is essential for consumer safety and product integrity—but in today's clean beauty landscape, we, as formulators, may feel under pressure to minimize traditional preservatives. That’s where Hurdle Technology comes in: a modern strategy that allows us to use multiple mild preservation strategies together, rather than relying on a single strong preservative. This is something new that I’ve just now learned, after 23 years of formulating. I always thought Tetrasodium EDTA & Germall Plus were good enough. While both are very effective, we can do even better.

But What is Hurdle Technology?

Hurdle Technology is a preservation method that uses a combination of "hurdles" to control microbial growth. Each hurdle targets microbes in a different way, and together they create an environment that is inhospitable for bacterial, yeast, and mold growth—without needing high concentrations of any single preservative.

The Key Hurdles in Skincare Formulation

1. Low Water Activity (aw):

   Reducing available water through humectants like glycerin, polyols (e.g., propanediol), or oils in waterless formulas inhibits microbial growth.

2. pH Control:

   Adjusting pH below 5 or above 9 can prevent growth of most microorganisms. Many natural preservatives work more effectively in lower pH ranges.

3. Chelating Agents:

   Ingredients like Disodium EDTA or Sodium Phytate bind metals that bacteria need to thrive, weakening their ability to reproduce.

4. Antimicrobial Boosters:

   Ingredients like caprylyl glycol, ethylhexylglycerin, and glyceryl caprylate enhance the performance of traditional preservatives and may have mild antimicrobial effects themselves.

5. Multifunctional Ingredients:

   Some active ingredients, like niacinamide, ferments, or organic acids, bring both skincare benefits and preservative-boosting properties.

6. Packaging Design:

   Airless pumps, single-use capsules, and tubes minimize air and finger contact, reducing microbial contamination risk.

🔹 Active Ingredients with Preservative-Boosting Properties

INCI Name	Primary Skin Benefit	Preservative-Boosting Action	Typical Use Rate
Niacinamide	Brightening, barrier repair	Alters microbial metabolism at acidic pH	2–5%
Gluconolactone	Gentle exfoliant, antioxidant	Chelator, acidifies water phase	0.5–2%
Sodium Benzoate (when paired with Gluconolactone)	Mild preservative	Synergizes with low pH boosters	0.2–1%
Sodium Levulinate	Humectant, antimicrobial	Disrupts microbial membrane at low pH	0.5–1%
Sodium Anisate	Anti-inflammatory	Antifungal properties at low pH	0.5–1%
Leuconostoc/Radish Root Ferment Filtrate	Moisturizing, probiotic-based	Produces antimicrobial peptides	1–4%
Lactobacillus Ferment	Soothing, barrier support	Produces bacteriocins	1–2%
Pentylene Glycol	Humectant	Weak antimicrobial, enhances phenoxyethanol	1–5%
Hydroxyacetophenone	Soothing, antioxidant	Boosts broad-spectrum preservatives	0.1–0.7%
Magnolol & Honokiol (Magnolia Bark Extract)	Antioxidant, anti-inflammatory	Strong antifungal and antibacterial	0.1–0.3%
Sodium Caproyl/Lauroyl Lactylate	Skin-conditioning	Mild antimicrobial synergist	0.2–1%
Propylene Glycol	Humectant, solvent	Reduces water activity, co-preservative	1–10%

Why Use Hurdle Technology?

• Lower preservative levels without compromising safety

• Cleaner labels and better alignment with natural or organic branding

• Custom preservation strategies for sensitive formulas like eye creams or baby care

• Improved consumer tolerance—fewer reports of irritation or sensitization

As an Example:

Let’s say you’re formulating a hydrating facial serum with hyaluronic acid and aloe. Instead of using 1% phenoxyethanol alone, you might combine:

• 0.8% Phenoxyethanol (not a stand alone preservative)

• 0.3% Ethylhexylglycerin (fungi protection)

• 0.3% Caprylyl Glycol (fungi protection)

• pH adjusted to 4.8-5

• 3% Glycerin for reduced water activity

• 2% Propanediol

• Disodium EDTA at 0.2% to chelate metals

• An airless pump bottle

Now let’s break down each individual hurdle section to get a better understanding.

🔹 LOW WATER ACTIVITY

“Starve the microbes.”

✅ What it is:

Water activity (not to be confused with moisture content) is a measurement of the free, unbound water in a formula that’s available to support microbial growth. It ranges from 0 (bone dry) to 1.0 (pure water). Most bacteria require a ≥ 0.91, while fungi and molds can survive around 0.70.

✅ Why it matters:

Microorganisms need water to grow, reproduce, and metabolize. If we reduce the water activity in a formulation—either by removing water or binding it—we create an inhospitable environment for microbes, which significantly reduces the risk of contamination and spoilage.

✅ Strategies to reduce water activity:

Method	Description	Example Ingredients
Anhydrous Formulation	Completely water-free products. No preservation usually needed.	Body balms, oil-based serums, lip butters
Water Binding Agents	Hygroscopic (water-attracting) ingredients that tie up free water.	Glycerin, Propylene Glycol, Sorbitol, Propanediol
Humectant-Heavy Systems	High humectant-to-water ratios limit microbial viability.	Toners or serums with ≥ 10% glycerin/propanediol
Water-in-Oil Emulsions	Less available water in external phase.	Rich creams, cold creams
High Sugar/Salt Content	Not common in cosmetics, but relevant for scrubs or masks.	Sugar scrubs, Dead Sea mud masks

✅ Formulation Considerations:

• Reducing is not the same as having no water.

• Adding humectants like glycerin affects viscosity and skin feel—balance is key.

• Be cautious: bound water still contributes to formula texture and stability but won't support microbial growth.

• 
  

·        🔹 pH CONTROL

·        “Make it uncomfortable for microbes.”

·        ✅ What it is:

·        pH is a measure of how acidic or basic (alkaline) a substance is, on a scale from 0 to 14. Most cosmetic formulations fall between pH 3.5 and 7. Microorganisms thrive best in neutral to slightly alkaline conditions (pH 6.5–7.5). By formulating outside of this optimal range, you can inhibit microbial growth.

·        ✅ Why it matters:

·        Many bacteria and fungi can’t survive or reproduce in low pH environments. Additionally, most natural and synthetic preservatives are only effective within certain pH ranges—often acidic. pH control not only deters microbes directly but also amplifies preservative efficacy.

·        ✅ Optimal pH Ranges for Skin & Preservatives:

Preservative	Effective pH Range
Phenoxyethanol	3.0–8.0
Sodium Benzoate	≤ 5.5
Potassium Sorbate	≤ 5.5
Gluconolactone & Sodium Benzoate	3.0–5.5
Dehydroacetic Acid	3.0–6.0
Organic Acids (e.g., levulinic, caprylic)	4.0–6.0
Euxyl PE 9010 (Phenoxyethanol + Ethylhexylglycerin)	3.0–8.5

✅ Strategies to Adjust & Control pH:

Method	Ingredient Type	Examples
Lower pH	Acids	Citric Acid, Lactic Acid, Gluconolactone
Raise pH	Bases/Alkalizers	Sodium Hydroxide, Potassium Hydroxide, TEA
Buffer pH	pH-stabilizing pairs	Sodium Citrate + Citric Acid (Citrate buffer)

✅ Formulation Tips:

• Always adjust pH in the water phase, after hydrating gums but before emulsification.

• Use a calibrated digital pH meter for accurate readings.

• Check pH again after emulsification and cooling, as heat and ingredient interaction can shift pH.

• If using acid-sensitive ingredients (e.g., peptides), buffer carefully to avoid degradation.

·        ✅ What Phenoxyethanol Controls:

Microbe Type	Effectiveness	Notes
Bacteria (Gram-positive & Gram-negative)	✅ Highly effective	Excellent for E. coli, Staph aureus, Pseudomonas, etc.
Yeast	⚠️ Moderate	May require a co-preservative to be reliably effective
Mold	⚠️ Moderate	Often weak alone—combine with antifungal boosters
Fungi (including molds & yeasts)	⚠️ Partial spectrum	Works better when combined with ethylhexylglycerin, sorbates, or caprylyl glycol

·        🔹 CHELATING AGENTS

·        “Take away the microbes’ survival tools.”

·        ✅ What it is:

·        Chelating agents are ingredients that bind metal ions (like calcium, magnesium, iron, and copper) present in water, botanical extracts, or raw materials. These trace metals can catalyze oxidation and fuel microbial growth. By removing them from the environment, chelators effectively weaken both oxidative degradation and microbial metabolism.

✅ Why it matters in preservation:

Metal ions can:

• Stabilize microbial cell walls

• Support enzymatic functions in bacteria and fungi

• Accelerate rancidity and breakdown of oils

Chelators inhibit these effects, making it harder for microbes to survive and helping to stabilize your product’s shelf life.

🔹 Effective Chelating Agents in Cosmetics

INCI Name	Source	Typical Use Rate	Natural Approved	Notes
Disodium EDTA	Synthetic	0.05–0.2%	❌ No	Highly effective; works across pH ranges; boosts preservative efficacy
Tetrasodium EDTA	Synthetic	0.05–0.2%	❌ No	Used in high pH formulas (like soaps and shampoos)
Sodium Phytate	Natural (rice bran)	0.05–0.5%	✅ Yes (EcoCert/COSMOS)	Excellent alternative to EDTA in natural products
Phytic Acid	Natural	0.05–0.5%	✅ Yes	Powerful natural chelator; often sold as 50% solution
Gluconolactone	Fermentation-derived	0.5–2%	✅ Yes (EcoCert)	Mild chelator + pH adjuster + preservative booster
Citric Acid	Natural (citrus)	0.05–0.5%	✅ Yes	Mild chelator; mainly used as a pH adjuster in water phase
Trisodium Ethylenediamine Disuccinate (EDDS)	Synthetic (biodegradable)	0.1–0.3%	✅ Yes (readily biodegradable)	Eco-friendlier alternative to EDTA; less widely available
Sodium Gluconate	Fermentation-derived	0.1–1%	✅ Yes	Biodegradable, multifunctional; less potent than EDTA
Sodium Citrate	Natural	0.05–0.5%	✅ Yes	Weak chelator; works best in buffered systems with citric acid

✅ How to Choose the Right Chelator:

• For conventional systems with preservatives:

  
  

  → Use Disodium EDTA or Tetrasodium EDTA for maximum efficacy.

• For natural or "clean" claims:

  
  

  → Opt for Sodium Phytate, Phytic Acid, or Gluconolactone.

• For pH-dependent systems or sensitive actives (like peptides):

  
  

  → Consider Citric Acid with Sodium Citrate for buffering.

✅ How They Enhance Preservation:

• Boost efficacy of broad-spectrum preservatives

• Reduce the need for higher preservative loads

• Improve clarity and color stability in aqueous products

• Assist in controlling microbial resistance

✅ Formulation Tips:

• Add to the water phase before heating

• Combine with low pH systems for even better preservation synergy

• For natural formulations, sodium phytate is a strong alternative to EDTA

• Ensure compatibility: chelators may impact certain emulsifiers or actives

🔹 ANTIMICROBIAL BOOSTERS

“Reinforce your preservative system.”

✅ What they are:

Antimicrobial boosters are multifunctional ingredients that aren’t traditional preservatives but still offer broad-spectrum antimicrobial support. They often work by:

• Disrupting microbial membranes

• Enhancing the penetration and efficacy of preservatives

• Creating inhospitable conditions for microbial survival

Used alone, they may not meet challenge test standards—but combined with preservatives and other hurdles, they reduce the required preservative load and improve performance.

✅ Common Cosmetic Antimicrobial Boosters:

Ingredient	Skin Feel	Typical Use Rate	Notes
Caprylyl Glycol	Silky, moisturizing	0.3–1.2%	Mild, broad-acting; disrupts membranes
Ethylhexylglycerin	Lightweight	0.3–1.0%	Reduces microbial resistance; boosts phenoxyethanol
Glyceryl Caprylate	Light emollient	0.3–1.0%	Emollient + co-emulsifier; effective against fungi
Hexylene Glycol	Light solvent	0.5–2%	Often used with phenoxyethanol in blends
Undecylene Glycol	Slippery, wet	0.2–1.0%	Effective against yeast/fungi
1,2-Hexanediol	Smooth, silky	0.5–1.0%	High-performance multifunctional active

✅ Benefits of Using Boosters:

• Allow for reduced preservative concentrations

• Provide moisturizing and emollient properties

• Offer natural label appeal in combination systems

• Improve performance at the formula’s pH and water activity levels

✅ Formulation Considerations:

• Compatible with both emulsions and surfactant systems

• Add to cool-down phase if heat-sensitive (check supplier guidelines)

• Test for preservative synergism in formulas with plant extracts or ferments

• Watch for solubility—some require emulsification or solvent carriers

·       

🔹 MULTIFUNCTIONAL INGREDIENTS

·        “Do more than preserve.”

·        ✅ What they are:

·        These are ingredients primarily added for their skincare benefits—hydration, soothing, brightening, or barrier support—but they also have secondary antimicrobial or preservation-boosting actions. In a Hurdle Technology system, they help reduce the microbial load and contribute to the product’s performance and marketing appeal.

·        ✅ Key Multifunctional Preservative-Boosters:

Ingredient	Primary Function	Preservative Role	Notes
Niacinamide (Vitamin B3)	Brightening, barrier repair	Alters microbial metabolism	Works best in synergy with low pH and chelators
Leuconostoc/Radish Root Ferment	Probiotic extract	Mild antimicrobial peptides	Ideal in natural formulations
Lactobacillus Ferment	Probiotic preservative	Produces bacteriocins	Compatible with acid systems
Gluconolactone	Gentle acid/exfoliant	Chelator + pH modifier	Boosts organic acid systems
Pentylene Glycol	Humectant, solvent	Weak antimicrobial effect	Enhances efficacy of phenoxyethanol blends
Hydroxyacetophenone	Antioxidant, soothing	Boosts efficacy of mild preservatives	Supports preservation in surfactant systems
Sodium Levulinate & Sodium Anisate	Natural acids	Disrupt microbial cell membranes	Used in "preservative-free" systems with pH < 5.5

✅ Benefits:

• Allow you to justify label claims like "brightening," "soothing," or "hydrating"

• Reduce reliance on synthetic or controversial preservatives

• Offer natural or eco-certified alternatives

• Create synergistic effects with low pH, chelators, and boosters

✅ Formulation Tips:

• Some ingredients (like ferments or acids) are pH-dependent

• These should be used in well-balanced systems with backup preservation if needed

• If working toward a “no added preservative” claim, these ingredients help maintain microbiological stability while meeting consumer-friendly labeling expectations

·       

🔹 PACKAGING DESIGN

·        “Don’t give microbes a way in.”

·        ✅ What it is:

·        Packaging is more than a vessel—it's an active component of your preservation system. Smart packaging choices can minimize contamination, extend shelf life, and enhance product safety without needing to increase preservative content.

·        ✅ Why it matters:

·        Even the most well-preserved formula can be compromised by poor packaging. Every time a user dips a finger, exposes product to air, or leaves the cap off, there’s an opportunity for contamination. Packaging that reduces exposure to air, moisture, fingers, and UV light directly supports preservation.

·        ✅ Preservation-Friendly Packaging Types:

Packaging	Benefits	Ideal For
Airless Pumps	No direct contact, no air exposure	Creams, lotions, serums
Tubes	Minimal air re-entry; product is protected	Gels, ointments, body care
Single-Use Capsules	100% contamination control	Actives, serums, eye treatments
Dropper Bottles	Minimal exposure if not touched	Face oils, watery serums
Spray Bottles (Fine Mist)	Hands-free dispensing	Toners, body sprays
Opaque & UV-Resistant Bottles	Prevent light-triggered degradation	Vitamin C, botanical-rich formulas

✅ Formulation Considerations:

• Choose packaging based on product sensitivity (e.g., oxygen-sensitive actives need airless)

• Consider material compatibility: certain ingredients can leach or degrade plastics

• For “natural” systems with reduced preservative loads, closed packaging is essential

• Add labels that encourage safe usage: “Use within 3 months,” “Keep lid closed,” etc.

·        ✅ Bonus Tip:

·        You can often formulate milder or "preservative-free" systems if you combine low pH, chelators, antimicrobial boosters, and protective packaging—especially in rinse-off or single-dose formats. That being said, I would highly recommend using hurdle technology with a broad spectrum preservative. It's your customers, let's keep them safe.

~Lissa~