Sensitization & Irritation — ISO 10993-10/-23 Endpoint Selection

Sensitization and irritation are distinct endpoints now addressed in separate standards: ISO 10993-10 for sensitization and ISO 10993-23 for irritation. Test selection should reflect the device's contact and the available chemical data before defaulting to animal studies.

Choose the endpoint from the contact

Skin, mucosal, ocular and intracutaneous exposure scenarios map to different irritation assessments, and sensitization addresses delayed hypersensitivity. The biological evaluation plan should state which endpoints remain open after chemistry review. In-vitro methods exist for some endpoints and may be acceptable depending on the device and market — confirm expectations with the assessor before commissioning animal work.

Agree extraction and dosing

Polar and non-polar extracts, exaggeration factors and dosing regimes affect the outcome. The protocol should record the extraction conditions, the rationale and the controls. Ask how borderline reactions are scored and how observer blinding and calibration are maintained.

Confirm editions and reporting

Irritation was separated from ISO 10993-10 into ISO 10993-23; confirm which editions the study plan cites and that reports state them explicitly. Where an in-vitro or read-across argument replaces a test, the justification — not just the omission — belongs in the evaluation file.

Choose endpoints only when the exposure warrants them

Cytotoxicity, sensitization and irritation are distinct endpoints, not interchangeable safety conclusions. Blood-contacting applications may require hemocompatibility evaluation; systemic toxicity is a separate risk-based endpoint rather than a universal panel. Agree extraction conditions, test article preparation, controls and interpretation with the evaluator. A pass on one endpoint does not establish complete biological safety.

What to include in your buyer brief

Start with the decision the work must support. Unknown details can be clarified after the initial inquiry.

Product, materials/formulation, patient or drug contact, contact duration, intended use and target market; identify changed materials, suppliers or processes.
Finished configuration, sample count and lots, sterilization modality/cycles, aging and storage history; justify worst-case variants and destructive allocations.
Existing evaluation plan, drawings, specifications, methods/editions, previous reports and acceptance criteria; send confidential files only through the private intake.
Required report, quality/accreditation scope, budget range, location, shipping constraints and decision deadline; ask the provider to explain exclusions and subcontracted work.

Sample considerations

Provide device materials, contact type/duration and existing chemical characterization.
State target markets and the endpoints the evaluation plan still requires.
Agree extraction conditions, study design, controls and reporting format.

Questions to ask a laboratory

Which endpoints require testing versus a documented data-based argument?
Which standard editions will the studies cite?
How are borderline findings scored and reported?

Laboratories with relevant capabilities

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Frequently asked questions

Are sensitisation and irritation the same endpoint?: No. They are separate endpoints addressed by different parts of the ISO 10993 family, and a device may need data for one and not the other.
Can irritation be assessed without animal testing?: In vitro approaches exist for some device types and extract categories, and their acceptance depends on the device and the requirement. Ask laboratories what they can support and what has been accepted for comparable devices.