Sanitary pad vaginal mucosal irritation testing is a critical biocompatibility evaluation that verifies whether extractable substances from feminine hygiene products cause inflammatory or irritant reactions in delicate mucosal tissue. The test is conducted in accordance with internationally recognized standards such as ISO 10993-23:2021 (formerly ISO 10993-10) and GB/T 16886.10, and it forms a key part of the safety documentation required by hygienic product standards including GB 15979. This article explains the testing principles, sample requirements, methodologies, scoring criteria, and practical applications for manufacturers and regulatory professionals.
Technical Overview
Sanitary pads, panty liners, and related absorbent hygiene products remain in prolonged and repeated contact with the vulvar region during menstruation. Surface materials, superabsorbent polymers, adhesives, and functional additives such as fragrances or plant extracts can migrate from the product to the surrounding mucous membranes. The vaginal mucous membrane irritation test is therefore a core component of the biological safety evaluation of these products, determining whether substances extracted from a finished product provoke inflammation, tissue damage, or other irritant reactions in mucosal tissue.
The evaluation follows the risk management framework of ISO 10993-1 and is performed in accordance with ISO 10993-23:2021 (Biological evaluation of medical devices — Part 23: Tests for irritation), which absorbed the intravaginal irritation method formerly published in ISO 10993-10:2010. In China, the equivalent method standard is GB/T 16886.10, while hygienic requirements for disposable hygiene products, including sanitary pads, are specified in GB 15979. Sample extraction is governed by ISO 10993-12 and its GB/T counterpart.
- Evaluation endpoint: irritant response of vaginal mucous membrane tissue
- Primary method standards: ISO 10993-23:2021 (formerly ISO 10993-10:2010) and GB/T 16886.10
- Extraction standards: ISO 10993-12 and GB/T 16886.12
- Product safety baseline: GB 15979, hygienic requirements for disposable hygiene products
Testing Samples
Finished Products
Complete sanitary pads of all formats, including regular, ultra-thin, overnight, winged, and organic-cotton products, as well as panty liners, can be evaluated. Finished-product testing assesses the combined effect of all materials, process residues, and additives. Products containing functional ingredients such as herbal extracts, fragrances, or cooling agents receive particular attention because these substances carry a higher inherent irritation potential.
Component and Raw Materials
Individual materials may be tested separately during development or supplier qualification. Typical components include top-sheet nonwoven fabrics made from polypropylene or polyethylene bicomponent fibers, transfer layers, fluff pulp and superabsorbent polymer cores, backsheet films, hot-melt adhesives, elastic elements, and release paper. Component-level testing helps isolate the source of any irritation observed in a finished product and supports raw material substitution decisions.
Test Extracts
Because the product contacts tissue externally rather than being implanted, testing is performed on extracts (eluates). Materials are cut into small pieces and extracted under standardized conditions, commonly at a ratio of 3 cm²/mL for surface-area-based sampling or 0.2 g/mL for mass-based sampling, using a polar solvent (0.9 percent sodium chloride solution) and, where justified, a non-polar solvent such as sesame or cottonseed oil. Extraction is typically conducted at 37°C for 72 hours or under accelerated conditions permitted by ISO 10993-12.
Testing Items
A comprehensive vaginal mucous membrane irritation evaluation generally includes the following items, which may be combined with other biocompatibility endpoints to build a complete biological safety profile:
- Intravaginal mucous membrane irritation index using the in vivo rabbit model, which is the core test item
- In vitro irritation screening using reconstructed human vaginal epithelium (RhVE) tissue models
- Complementary biological endpoints, including in vitro cytotoxicity (ISO 10993-5) and skin sensitization (ISO 10993-10:2021)
- Supporting physicochemical checks such as pH, residual additives, and extractable screening to assist in interpreting the biological result
- Microbiological limits required by GB 15979, including total bacterial count, coliforms, fungal counts, and pathogenic bacteria
Testing Methods
Sample Preparation and Extraction
Test articles and control articles are prepared under aseptic conditions. Extraction is performed in parallel with polar and non-polar media, together with solvent-only blanks that serve as negative controls. The extraction ratio, temperature, and duration are selected so that the resulting extract is representative of the leachables a user might be exposed to under worst-case yet physiologically plausible conditions. Extracts are applied promptly after preparation to prevent degradation or changes in composition.
In Vivo Intravaginal Irritation Test (Rabbit Model)
The classical method, described in ISO 10993-23:2021 and previously in ISO 10993-10:2010, as well as in GB/T 16886.10, uses healthy adult female rabbits. A typical protocol assigns at least three animals to the test group and three to the control group. One milliliter of the test extract is instilled gently into the vagina using a smooth-tipped catheter once daily for five consecutive days, while control animals receive the corresponding blank solvent. Clinical observations, including general condition, food consumption, behavior, vaginal discharge, and body weight, are recorded throughout the exposure period. Approximately 24 hours after the final dose, animals are humanely euthanized and the vaginal tissues are collected for evaluation.
Histopathological Evaluation and Irritation Scoring
The excised vaginal tissue is examined macroscopically and then processed for histology through formalin fixation, paraffin embedding, and hematoxylin-and-eosin staining. A qualified pathologist scores four histological parameters, namely epithelial integrity (including ulceration or loss), leukocyte infiltration, vascular congestion, and edema, each on a graded scale. Parameter scores are summed for each animal and averaged across the group to obtain the irritation index. An average score consistent with no reaction indicates a non-irrigant, or negligible, response, while higher average scores are classified as slight, moderate, or severe irritation according to the boundaries defined in the standard. If the control group shows an unexpected reaction, results are interpreted against the concurrent control and the study may be repeated with an alternative extraction condition.
In Vitro Alternative Methods
To support the principles of replacement, reduction, and refinement of animal testing, three-dimensional reconstructed human vaginal epithelium models are increasingly used. Test extracts or dosing solutions are applied directly to the apical surface of the tissue cultures, and cell viability is measured photometrically, for example by MTT conversion, after defined exposure periods. Results can be expressed as tissue viability percentage or as the exposure time that reduces viability by 50 percent. In vitro methods are well suited to screening formulations and materials during development, and their regulatory acceptance for mucosal irritation endpoints continues to expand, although many submissions still rely on, or supplement, the in vivo rabbit test for confirmatory evidence.
Applications
Vaginal mucous membrane irritation testing supports manufacturers across the entire product life cycle of sanitary pads and related feminine hygiene products:
- Regulatory compliance: demonstrating conformance with the toxicological evaluation requirements of GB 15979 for disposable hygiene products and satisfying market surveillance or product documentation obligations in various jurisdictions
- Research and development: comparing new top-sheet materials, superabsorbent polymers, adhesives, or functional additives before commercial scale-up
- Quality control: verifying periodically that production batches and supplier changes do not alter the biological safety profile of the product
- Claims substantiation: providing objective evidence that supports gentle-use, sensitive-skin, or non-irritating product positioning statements
- Complaint and incident investigation: diagnosing the biological basis of consumer-reported discomfort or adverse reactions
- Market access: supplying the technical documentation requested by importers, retailers, and regulators for domestic and export sales
Manufacturers are advised to have testing performed by accredited third-party laboratories operating under recognized laboratory quality management systems, so that the results are widely accepted by regulators and trading partners worldwide.
FAQ
Question: Why do sanitary pads need a vaginal mucous membrane irritation test?
Answer: Sanitary pads remain in close, prolonged contact with mucosal tissue during use. The test confirms that extractable substances from the product do not provoke irritation or inflammation, which is a fundamental safety expectation and a common requirement under hygienic product standards such as GB 15979.
Question: Which standards govern the test?
Answer: The in vivo intravaginal irritation method is specified in ISO 10993-23:2021, which superseded the corresponding method in ISO 10993-10:2010, and in GB/T 16886.10. Sample extraction follows ISO 10993-12, while overall product hygiene requirements follow GB 15979.
Question: Why are both saline and vegetable oil extracts used?
Answer: Saline extracts hydrophilic, polar substances such as salts and water-soluble residues, while vegetable oil extracts lipophilic, non-polar substances such as plasticizers, oils, and certain additives. Running both solvents in parallel ensures the evaluation covers the full range of possible leachables.
Question: Is animal testing always required?
Answer: No. In vitro reconstructed human vaginal epithelium models provide an animal-free screening option consistent with the 3Rs principles. Regulatory acceptance of in vitro data varies by jurisdiction and claim, so many development programs use in vitro screening first and confirm findings with the in vivo rabbit test when required.
Question: What result counts as a pass?
Answer: A product is generally considered acceptable when the irritation index indicates a non-irrigant or negligible response that is comparable to the blank control. Results classified as slight, moderate, or severe irritation typically require formulation review, material substitution, or further investigation before the product can proceed.
Question: How much sample is needed and how long does testing take?
Answer: A typical study requires roughly 30 to 60 finished pads or an equivalent quantity of component materials to provide sufficient extract volume for the dosing schedule and any repeat testing. The full cycle, including extraction, animal dosing, histopathological evaluation, and reporting, usually takes four to six weeks, while in vitro screening can often be completed in two to three weeks.
