Propolis

Propolis is one of the oldest natural antiseptics known to humans. Ancient Egyptians used it in embalming. Hippocrates applied it to wounds. But only in recent decades have we had the tools to understand why it works, at what concentrations, and what you can realistically expect from it — as opposed to what marketing copy claims.

What It Is

Propolis is a resinous substance produced by honeybees (Apis mellifera) from plant sources: tree buds (especially poplar), pine and fir resins, and bark. Bees blend these resins with their own glandular secretions and beeswax to create what the Greeks called pro-polis — literally "before the city," a defence for the hive. Its biological role is to seal cracks, sterilise the interior, and prevent microbial and fungal growth in the warm, nutrient-rich hive environment.

The chemical composition of propolis varies by geography, season, and local flora — Brazilian propolis differs significantly from European or Chinese propolis. However, its core structure is consistent: 50–55% resins and balsams, 25–35% wax, 10% essential oils, and 5% pollen. The resin fraction carries most of the biological activity.

The key active compounds are polyphenols: flavonoids (kaempferol, quercetin, apigenin, chrysin, naringenin) and phenolic acids, most notably caffeic acid phenethyl ester (CAPE) along with ferulic and coumaric acids. CAPE is among the best-studied individual molecules in propolis.

The INCI designation Propolis Extract covers a wide range of preparations — ethanolic, aqueous, or dry. Ethanolic extracts generally contain higher flavonoid concentrations and show stronger antibacterial activity than water-based alternatives.

How It Works

The antibacterial action of propolis is not driven by a single compound but by several parallel mechanisms.

Membrane disruption. Flavonoids and phenolic acids integrate into bacterial lipid bilayers, increasing membrane permeability. K⁺ and Mg²⁺ ions leak out, membrane potential collapses, and the bacterium can no longer sustain normal metabolism. This mechanism has been documented for Streptococcus mutans, Streptococcus sobrinus, and Porphyromonas gingivalis.

Glucosyltransferase (GTF) inhibition. S. mutans uses the enzyme GTF to synthesise glucans from sucrose — the structural scaffold of dental plaque that anchors bacteria to tooth surfaces. Propolis flavonoids inhibit GTF activity, reducing both adhesion and biofilm formation. This directly targets the cariogenic mechanism.

Anti-inflammatory pathway. CAPE inhibits NF-κB, the master transcription factor for inflammation. The downstream result is reduced production of IL-1β, IL-6, and TNF-α in periodontal cells — which explains the reduction in gingival bleeding observed in clinical trials.

Antioxidant activity. Propolis flavonoids scavenge reactive oxygen species in inflamed gingival tissue, reducing oxidative damage to periodontal structures.

Clinical Evidence

A 2025 systematic review and meta-analysis (Sycińska-Dziarnowska et al., PMID 41003407) synthesised trials of propolis mouthwashes and toothpastes and confirmed statistically significant reductions in Plaque Index and Gingival Index compared to placebo.

A phase II randomised clinical trial (Pereira et al., 2011, PMID 21584253) — one of the most cited studies — enrolled patients with gingivitis who used a 1% propolis mouthwash for 45 days. Both Plaque Index and Gingival Bleeding Index decreased significantly versus baseline.

A direct head-to-head randomised trial (PMC10998313) compared propolis mouthwash to 0.12% chlorhexidine and found comparable efficacy in reducing plaque and gingivitis scores. Propolis showed no staining, no altered taste, and no detectable disruption to oral microbiota — common drawbacks of long-term chlorhexidine use.

In orthodontic patients — a high-plaque-risk population — a propolis mouthwash significantly reduced plaque and gingival inflammation versus control over 4 weeks (Dehghani et al., 2019, PMID 31001394).

On the toothpaste side, a clinico-microbiological study (Mohsin et al., 2015, PMID 25733780) found that a propolis-containing dentifrice significantly reduced salivary S. mutans counts at weeks 3 and 4 (p<0.05).

Working concentrations:

| Form | Studied range | Clinically effective | |---|---|---| | Mouthwash | 0.5–5% | ≥1% | | Toothpaste | 3–10% | ≥3% | | Dental varnish/gel | 5–30% | ≥5% |

Critical caveat: standardisation of propolis extracts is the field's main problem. Studies use extracts with flavonoid content ranging from 5% to over 30%. A percentage concentration without standardisation tells you little about actual activity. Reputable suppliers specify total flavonoid content of the extract.

Safety

Propolis is well-tolerated topically in the oral cavity at hygiene-product concentrations. No systemic toxicity has been reported at these use levels.

Main risk: allergy. Contact allergy to propolis affects an estimated 1.2–6.6% of the population based on patch-test databases. Cases of allergic stomatitis and cheilitis have been documented in dental practice. Cross-reactivity with balsam of Peru is possible.

Regulatory status:

• EU Cosmetics Regulation: permitted (not listed in Annex II or III restricted substances).
• FDA: GRAS for food use; not restricted in cosmetics.
• Pregnancy/lactation: insufficient data; caution advised for prolonged use.

Formulation note: flavonoids in propolis can oxidise at high pH. Acidic to neutral formulas (pH 5.5–7) preserve activity better.

QDRO Position

Under consideration for a dedicated natural-antibacterial line. Requirements for a viable formula: standardised extract with documented flavonoid content (minimum 5%), concentration of at least 1% in rinses or 3% in paste, and confirmed pH compatibility. Allergen warning required on packaging for the proportion of users with propolis sensitivity.

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Sources:

• Sycińska-Dziarnowska M et al. (2025). Propolis as a Natural Remedy in Reducing Dental Plaque and Gingival Inflammation: A Systematic Review and Meta-Analysis. J Funct Biomater. PMID: 41003407
• Pereira EM et al. (2011). Clinical Evidence of the Efficacy of a Mouthwash Containing Propolis for the Control of Plaque and Gingivitis: A Phase II Study. Evid Based Complement Alternat Med. PMID: 21584253
• Dehghani M et al. (2019). Effect of Propolis mouthwash on plaque and gingival indices over fixed orthodontic patients. J Clin Exp Dent. 11(3):e244-e249. PMID: 31001394
• Mohsin S et al. (2015). The Effects of a Dentifrice Containing Propolis on Mutans Streptococci: A Clinico-Microbiological Study. Ethiop J Health Sci. 25(1):9-16. PMID: 25733780
• Botushanov PI et al. (2001). A clinical study of a silicate toothpaste with extract from propolis. Folia Med (Plovdiv). PMID: 15354462