Preservative Selection Guide

Choosing the Right Preservative for Your Cosmetic Products

Any cosmetic product that contains water — or ingredients derived from water like aloe vera juice, hydrosols, or floral waters — is at risk of microbial contamination. Water combined with organic ingredients creates an ideal environment for bacteria, yeast, and mold to thrive. Without a preservative, these products can become unsafe within days.

It is important to understand that preservatives and antioxidants serve different purposes. Preservatives prevent microbial growth in water-containing products. Antioxidants (like Vitamin E or rosemary oleoresin extract) prevent oils from going rancid through oxidation. A product may need one, the other, or both — but they are never interchangeable.

When Do You Need a Preservative?

You NEED a preservative when your product contains:

Water in any form (distilled, deionized, tap)
Aloe vera juice or gel
Hydrosols or floral waters
Any water-soluble extracts or infusions
Products that will contact wet hands (sugar scrubs, shower products)

Anhydrous products (lip balms, body butters, oil serums, salves) do NOT typically need a preservative because they contain no water. However, if the product will regularly contact wet hands or be stored in humid environments, consider adding one as a precaution.

Broad-Spectrum Coverage

An effective preservative system must provide broad-spectrum coverage, meaning it protects against all three types of microorganisms:

Bacteria

Including gram-positive (like Staphylococcus) and gram-negative (like Pseudomonas) bacteria. Gram-negative bacteria are particularly dangerous and harder to kill.

Yeast

Yeasts like Candida albicans can cause product spoilage and are common environmental contaminants.

Mold

Molds like Aspergillus niger grow readily in moist environments and can produce visible colonies and off-odors in products.

Some preservatives only cover one or two types. For example, Potassium Sorbate is effective against yeast and mold but weak against bacteria. That is why it is often paired with Sodium Benzoate, which covers bacteria. Always verify that your chosen system covers all three categories.

Common Preservative Systems

All preservatives listed below are available in the Soap Math Lotion Calculator. Usage rates and pH ranges reflect the data in our calculator database.

Euxyl PE 9010

INCI: Phenoxyethanol (and) Ethylhexylglycerin

Coverage: Broad-spectrum — Gram-positive bacteria, Gram-negative bacteria, yeast; partial mold coverage.
pH Range: 3–10 (most effective 4–7)
Usage Rate: 0.5–1.1% (optimal at 1%)
Composition: Pre-blended — 90% Phenoxyethanol, 10% Ethylhexylglycerin.
Phase: Cool-down (below 50°C / 122°F)
Notes: One of the most widely used preservative systems. Paraben-free and formaldehyde-free. Compatible with anionic, cationic, and nonionic systems. Ethylhexylglycerin acts as a skin-conditioning booster that disrupts microbial cell membranes. EU limits Phenoxyethanol to 1% max total.

Euxyl K 703

INCI: Phenoxyethanol (and) Benzoic Acid (and) Dehydroacetic Acid

Coverage: Broad-spectrum — Gram-positive bacteria, Gram-negative bacteria, yeast, mold.
pH Range: 3–6 (stable range); effective up to pH 8
Usage Rate: 0.6–1%
Composition: 81% Phenoxyethanol, 12% Benzoic Acid, 7% Dehydroacetic Acid.
Phase: Cool-down
Notes: Paraben-free. The organic acids (benzoic acid, dehydroacetic acid) provide strong antifungal activity, giving better mold coverage than PE 9010. Best performance at pH 3–6 where the organic acids are most active. Good all-around choice for lotions and creams.

Optiphen

INCI: Phenoxyethanol (and) Caprylyl Glycol

Coverage: Partial spectrum — Gram-positive bacteria, partial Gram-negative; yeast, mold.
pH Range: 4–8
Usage Rate: 0.75–1.5%
Composition: 58% Phenoxyethanol, 42% Caprylyl Glycol.
Phase: Cool-down
Notes: Paraben-free and formaldehyde-free. Can thin emulsions — always add during cool-down. Oil-soluble. Weaker Gram-negative coverage compared to Optiphen Plus or Euxyl PE 9010, so consider pairing with a chelator like EDTA for broader protection.

Optiphen Plus

INCI: Phenoxyethanol (and) Caprylyl Glycol (and) Sorbic Acid

Coverage: Broad-spectrum — Gram-positive bacteria, Gram-negative bacteria, yeast; partial mold.
pH Range: 3–6 (best below pH 6)
Usage Rate: 0.75–1.5%
Composition: 52.3% Phenoxyethanol, 41.7% Caprylyl Glycol, 6% Sorbic Acid.
Phase: Cool-down (add below 60°C / 140°F)
Notes: Paraben-free, formaldehyde-free, heat-stable. Sorbic acid boosts antifungal activity. NOT compatible with Carbomer-based formulations (sorbic acid reacts with carbomer). Good for thicker creams and emulsions.

Liquid Germall Plus

INCI: Propylene Glycol (and) Diazolidinyl Urea (and) Iodopropynyl Butylcarbamate

Coverage: Broad-spectrum — very effective against Gram-positive, Gram-negative bacteria, yeast, and mold.
pH Range: 3–8
Usage Rate: 0.1–0.5%
Composition: 59.4% Diazolidinyl Urea, 39.6% Propylene Glycol, 1% Iodopropynyl Butylcarbamate.
Phase: Cool-down — must add below 50°C (122°F)
Notes: Very effective at low concentrations. Water-soluble and easy to incorporate. Diazolidinyl Urea is a formaldehyde releaser — some consumers avoid this. Heat-sensitive, so never add to hot phases. Works well in emulsions, surfactant systems, and even highly pigmented products.

Germall Plus (Powder)

INCI: Diazolidinyl Urea (and) Iodopropynyl Butylcarbamate

Coverage: Broad-spectrum — Gram-positive bacteria, Gram-negative bacteria, yeast, mold.
pH Range: 3–8
Usage Rate: 0.05–0.2%
Composition: 99% Diazolidinyl Urea, 1% Iodopropynyl Butylcarbamate.
Phase: Cool-down — dissolve in water phase below 50°C
Notes: More concentrated than the liquid form. Contains a formaldehyde releaser. Hygroscopic powder — store in dry conditions. Very effective at extremely low usage rates.

Phenonip

INCI: Phenoxyethanol (and) Methylparaben (and) Propylparaben (and) Butylparaben

Coverage: Broad-spectrum — Gram-positive bacteria, Gram-negative bacteria, yeast, mold.
pH Range: 3–8
Usage Rate: 0.5–1%
Composition: 73% Phenoxyethanol, 15% Methylparaben, 8% Propylparaben, 4% Butylparaben.
Phase: Oil phase or cool-down
Notes: Oil-soluble — excellent for anhydrous products and balms. Contains parabens, which some consumers prefer to avoid. Very well-tested and reliable. One of the easiest preservatives to incorporate since it dissolves directly in the oil phase.

Potassium Sorbate + Sodium Benzoate

INCI: Potassium Sorbate + Sodium Benzoate (used together)

Coverage: Together they provide broad-spectrum coverage. Potassium Sorbate targets yeast and mold; Sodium Benzoate targets yeast, mold, and partial bacteria.
pH Range: Below 5.5 (Potassium Sorbate most effective at pH 4.4; Sodium Benzoate below pH 5)
Usage Rate: 0.1–0.5% each (Potassium Sorbate) and 0.1–0.5% (Sodium Benzoate)
Phase: Water phase — dissolve before combining
Notes: Considered more "natural" by consumers (both are food-grade, GRAS). Must be used at low pH — completely ineffective above pH 5.5. Do NOT combine Sodium Benzoate with Vitamin C (can form benzene). Often used in toners, micellar waters, and acidic formulations. Potassium Sorbate can sublime above 60°C, so add below that temperature.

Geogard Ultra

INCI: Gluconolactone (and) Sodium Benzoate

Coverage: Partial — partial Gram-positive, partial Gram-negative, partial yeast, partial mold.
pH Range: 3–5 (very pH-dependent)
Usage Rate: 0.6–1.2%
Composition: 74.25% Gluconolactone, 24.75% Sodium Benzoate, 1% Calcium Gluconate.
Phase: Water phase
Notes: ECOCERT and COSMOS approved — one of the few certified-natural preservative options. White powder. Only effective at low pH, and coverage is partial across all categories, so it may need boosting for robust preservation. Best for products with naturally low pH like toners and AHA serums.

Phenoxyethanol (standalone)

INCI: Phenoxyethanol

Coverage: Partial — strong against Gram-negative bacteria and yeast; partial Gram-positive coverage. Weak against mold alone.
pH Range: 3–10
Usage Rate: 0.5–1%
Phase: Cool-down (below 60°C / 140°F)
Notes: When used alone, Phenoxyethanol is NOT broad-spectrum — it needs a booster or secondary preservative for full coverage. This is why most pre-blended systems (like Euxyl PE 9010, Optiphen, or Phenonip) pair it with other actives. Compatible with anionic, cationic, and nonionic surfactant systems.

How to Choose

Use your product's pH as the primary decision factor:

pH above 6: Liquid Germall Plus or Germall Plus (Powder) — one of the few systems that works well at higher pH values (effective up to pH 8).

pH 4–8: Optiphen — paraben-free, oil-soluble, but consider pairing with a chelator for better Gram-negative coverage.

pH 3–6: Optiphen Plus — broader coverage than regular Optiphen, but NOT compatible with Carbomer gels.

Broad pH range (3–10): Euxyl PE 9010 — versatile, paraben-free, well-tested across almost any formula type.

Broad pH + full mold coverage: Euxyl K 703 or Phenonip — both provide full mold coverage that PE 9010 only partially covers. Phenonip contains parabens but is oil-soluble, making it ideal for anhydrous products.

Natural / clean-label (pH below 5): Potassium Sorbate + Sodium Benzoate or Geogard Ultra — considered more natural, but only effective in acidic formulas. Geogard Ultra is ECOCERT/COSMOS certified.

Important: Always check your product's pH after formulation. A preservative that requires low pH will fail in a neutral or alkaline product, no matter how much you add.

Common Mistakes

Using antioxidants as preservatives: Vitamin E and ROE prevent oil rancidity — they do NOT kill bacteria, yeast, or mold. A lotion preserved only with Vitamin E will grow dangerous microbes.

Relying on essential oils: Tea tree, lavender, and other essential oils have some antimicrobial activity in lab tests, but they cannot reliably preserve a cosmetic product at safe skin concentrations.

Not using enough preservative: Always follow the manufacturer's recommended usage rate. Under-dosing creates a product that appears fine initially but fails over time as microbial populations grow.

Wrong pH for your preservative: Each preservative has an effective pH range. Using Potassium Sorbate in a pH 7 lotion or Optiphen in a pH 8 product renders them ineffective.

Tips for Effective Preservation

Always measure your product's pH after formulating — before and after adding the preservative.
Add heat-sensitive preservatives (like Germall Plus) during cool-down, below 50°C (122°F).
Practice good manufacturing hygiene: sanitize equipment, use distilled water, and work in a clean environment.
Use airless pump bottles or tubes when possible — they reduce contamination compared to open jars.
If selling products, invest in challenge testing to verify your preservative system is effective.
Store finished products away from heat and direct sunlight to support preservative longevity.

Frequently Asked Questions

Related Resources

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