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CGR-ES-105 / EDITION 10.0

Boric acid/tannic acid foot powder with thymol

Cutaneous powder for soles · Spain · AEMPS

2026-10-14Reference document · Local adoption required

Collection and scientific editing: Stasinos Chr. SikaliasContent edition: 10.0Record editorial review date: 2026-10-14

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REFERENCE FORMULA

Reference formula

Reference basis: 100 g τελικού προϊόντος /100 g final product

IngredientSource quantityScaled quantity
Boric acid10 g—
Tannic acid5 g—
Heavy kaolin15 g—
Zinc oxide20 g—
Thymol1 g—
Ethanol 96%1 mL—
Talcq.s. ad 100 g—

Prerequisite formulations

No separate prerequisite monograph is listed.

Documentation

Preparation description
Beige cutaneous powder with a slight thymol odour. Per 100 g it contains boric acid 10 g, tannic acid 5 g, kaolin 15 g, ZnO 20 g and thymol 1 g, with 1 mL ethanol 96% and talc to final mass. [1]
Action and use
The source indication is plantar hyperhidrosis. This is a defined historical absorbent/astringent formula, not evidence of first-line status or treatment of fungal infection. Selection requires current boron, skin-integrity and alternative-treatment appraisal [2,8]. [1], [2], [8]
Specifications
Final mass 100 g; uniform beige powder without visible wet pockets or aggregates. Boric acid 10% and thymol 1% w/w. Particle size, moisture and residual ethanol limits are not supplied; visual inspection does not prove content uniformity. [1]
Light
The source leaflet requires protection from light and heat. Use a closed light-protective container with controlled powder dispensing. [1]
Air and oxidation
Close after use to limit volatile loss and airborne powder. The source does not prescribe airing to evaporate ethanol; do not introduce an arbitrary drying stage. [1]
Water and solubility
No separate water is added, but ethanol 96% contains water. The formula is not demonstrated anhydrous or low-aw. Wet equipment or damp feet can cause agglomeration. [1]
Humidity
The source requires moisture protection. Keep containers closed and equipment dry. Check flow/caking before release; there is no numerical finished-moisture limit. [1]
Temperature
Store below 30 °C. Prepare without heating, dissolving thymol in the specified ethanol. Remove ignition sources during ethanol handling [5]. [1], [5]
pH and compatibility
No direct pH specification exists for the powder. Tannic and boric acids do not define a numerical pH without a specified aqueous dispersion. Do not add neutraliser or buffer. [1]
Other interactions
Thymol is incompatible with menthol, camphor, alkalis and oxidisers [4]. Do not mix with mentholated talc in the same container. Ethanol is a flammable manufacturing solvent; this does not automatically classify the finished mixture [5]. [4], [5]
Ingredient-specific information
Use heavy kaolin as specified. Require pharmacopoeial talc with documented mineral-impurity controls; cosmetic/industrial grade is insufficient. FDA documents possible asbestos contamination of talc, not suitability of this batch [7]. [1], [7]
Staff protection
Use local extraction for weighing/mixing, gloves, coat and eye protection. Avoid dust clouds and clean without resuspending solids. Check boric acid, thymol and ethanol SDSs [3,5,10]. [3], [5], [10]
Risk assessment
Powder inhalation and application to damaged soles are critical risks. Each g contains 100 mg boric acid≈17.5 mg B, not absorbed dose [2]. Assess daily quantity, skin condition, duration, age and pregnancy. IARC classifies talc as probably carcinogenic, Group 2A; this identifies a substance hazard without quantifying risk from this use [6]. [1], [2], [6]
Compounding conditions
Weigh each solid separately. The five specified solids total 51 g. Talc q.s. refers to 100 g final product including added ethanol; do not automatically enter 49 g talc. Document mass balance and actual vehicle quantity. [1]
BUD rationale
The source gives 3 months protected from moisture below 30 °C. Reference ceiling: earlier of 89 days/3 calendar months, conditional on exact formula, suitable package and locally approved controls. No matched study, aw measurement or evidence of complete ethanol evaporation was found. A general 180-day solid limit is not automatically adopted. Any earlier raw-material expiry or documented in-use limit prevails. Editorial convention: calendar-month source periods are retained as calendar periods; the calendar-period conversion ceiling is 28 days for one month or 89 days for three months; a separately selected shorter ceiling still governs. It is a conservative conversion, not a source quotation. [1]
Prerequisites
No compounded-base dependency. Use source-specified boric acid, tannic acid, heavy kaolin, ZnO, thymol, ethanol 96% and talc. Do not replace thymol with thyme essential oil. [1]
Equipment
Balance, mortar/pestle or suitable powder blender, device for 1 mL ethanol, small closable thymol-dissolution vessel and powder dispenser. Work under extraction with ignition-source control. [1], [5], [10]
Compounding method
Mix tannic acid, boric acid, kaolin, ZnO and calculated talc uniformly. Dissolve 1 g thymol in 1 mL ethanol 96%. Gradually incorporate into the powder blend and homogenise. Verify 100 g final mass and uniformity. Evaporation, heating or ethanol removal is not prescribed. [1]
Observations
Antiseptic ingredients do not make the powder sterile or establish treatment of infection. This 1% thymol preparation is not interchangeable with another foot powder. Investigate unusual colour or wet lumps. [1]
Container and packaging
Use a tightly closable powder dispenser protecting from moisture/light. The outlet should limit aerosolised clouds. Record material; the source specifies no particular polymer or glass. [1]
Quality control
Check identity/amounts, heavy kaolin, ethanol 96%, final mass, uniform beige colour and absence of wet aggregates. Document mixing for uniformity. Talc impurity control requires certification/suitable testing, not visual inspection. [1], [7]
Storage
Keep closed and dry, protected from light, below 30 °C. Avoid humid bathroom storage; keep away from children and food products. [1]
Dispensing
For a small area of intact plantar skin only after assessment. The source excludes children under 3 years without automatically clearing older children. Avoid eyes, mucosa, wounds, burns and inhalation. Pregnancy/breastfeeding requires medical review; do not apply to breasts. Contraindicated in hypersensitivity to any ingredient. [1], [2], [8]
Labelling
FOOT POWDER — SOLES ONLY. Contains boric acid 10% and thymol 1%. Do not inhale/swallow. No wounds or mucosa. Quantity/duration: ___. Batch/prepared/use by: ___. Keep closed, dry, below 30 °C, away from children. [1]
v9_controls
The numeric value is a literature reference ceiling subject to its specific conditions. No actual batch BUD has been assigned and no aw measurements have been produced. The exact formula, prerequisites, container, storage and quality evidence require approval for the actual application. The BUD clock starts when compounding begins. Use the shortest applicable supported limit and assess in-use dating separately. USP categories are a technical framework and are not presented as Greek legislation.

Sources and references

  1. AEMPS — Formulario Nacional: POLVOS PÉDICOS (FN/2006/PO/040)2006 source code; current standalone PDF accessed 2026PDF pp.2–3, §§3–12 and patient leafletExact formula, process, finished appearance, source dating and route-specific precautions.2026-10-14
  2. EMA — Questions and answers on boric acid and borates used as excipients, Rev.1Adopted 11 November 2021; published 26 July 2022pp.3–6; §3, §5 and conversion annexBoron toxicity, age-related exposure warnings and conversion factors. Excipient guidance informs safety appraisal; not authorisation of these boron-active preparations.2026-10-13
  3. ILO/WHO — ICSC 0991: Boric acidApril 2014Prevention; chemical dangers; exposure effectsCAS 10043-35-3; occupational dust and reproductive hazards; raw-material precautions.2026-10-13
  4. AEMPS — FN/2003/PA/037: Timol2003 source code; current standalone PDFPDF p.2 §§3–10Thymol solubility, ingestion hazard and incompatibilities; does not establish efficacy or BUD of the powder.2026-10-13
  5. CDC/NIOSH — Ethyl alcoholPocket Guide page reviewed 30 October 2019Physical properties; flammability; incompatibilitiesEthanol raw solvent hazard; not a measured classification of the finished powder.2026-10-13
  6. IARC — Volume 136: evaluation of talc and acrylonitrile5 July 2024pp.1–3, talc evaluationTalc Group 2A hazard evaluation; separate from asbestos-containing talc. Hazard classification is not an individual dose-risk estimate.2026-10-13
  7. FDA — TalcCurrent page accessed 13 October 2026Asbestos: what it is and how to prevent its occurrence; testing summariesPotential asbestos contamination and importance of material selection/testing. Cosmetic surveillance does not validate a pharmaceutical batch.2026-10-13
  8. ABDA/AMK — Bedenkliche Rezepturarzneimittel, Stand Juni 20251 July 2025Recommendations; table entry Borsäure sowie deren Ester und SalzePrimary professional safety position: benefit–risk concerns and boron thresholds. German context, not Greek law and not a globally binding ban.2026-10-13
  9. Medsafe — Boron-containing excipients and fertility concerns, MARC 18610 June 2021pp.4–6, 14–18Regulatory evidence review and absorption uncertainty; its quoted 2017 warning wording is superseded by EMA Rev.1.2026-10-13
  10. CDC/NIOSH — Talc, containing no asbestos and less than 1% quartzPocket Guide page accessed 13 October 2026Exposure routes, symptoms, target organs, preventionOccupational respirable-dust hazard; not NIOSH hazardous-drug classification.2026-10-13
  11. USP — General Chapter <795> Frequently Asked QuestionsNovember 1, 2023 FAQ; rechecked 14 October 2026Questions 52, 54–56, 61, 64–66General category/extension rules only; not exact-product stability evidence.2026-10-14