Oak Bark (Quercus spp.): Traditional Uses, Tannin Chemistry & Modern Evidence

Oak bark (cortex Quercus) is rich in hydrolyzable tannins (gallotannins, ellagitannins) and condensed tannins (proanthocyanidins) — astringent, antimicrobial, anti-inflammatory.

Traditional Indications

• GI: Acute diarrhea, dysentery (astringent reduces secretion, binds toxins).
• Topical: Burns, wounds, ulcers, hemorrhoids, eczema, psoriasis, frostbite, excessive sweating (hyperhidrosis), mouth/throat inflammation (gargle).
• Other: Varicose veins (compress), foot baths for odor.

Preparations

• Decoction: 1 tsp bark / cup water, simmer 10–15 min. Drink 3×/day (diarrhea) or use as wash/compress.
• Tincture: 1:5 in 40% ethanol; 2–4 mL 3×/day.
• Ointment/Salve: 10–20% bark extract in base.

Evidence & Safety

• In vitro: antiviral, antibacterial, antioxidant, anti-inflammatory.
• Human data: limited; some RCTs for oral mucositis, hemorrhoids, atopic dermatitis (oak bark extract creams).
• Cautions: Tannins inhibit iron/mineral absorption (separate from meals). Avoid prolonged internal use (>2 wks) — hepatic/renal theoretical risk. Not in pregnancy/lactation (insufficient data). Topical: patch test.

Oak bark is a classic astringent; modern phytotherapy uses standardized extracts for defined indications.