When this test applies
Part of the baseline battery for essentially every patient-contacting device under ISO 10993-1:2025, alongside cytotoxicity and sensitization. Intracutaneous reactivity is the default route where a more specific irritation model — ocular, dermal, mucosal — is not indicated by the contact site.
When to run it
After cytotoxicity, and usually in the same submission as sensitization. Both use extracts prepared the same way, so running them together saves a round of sample preparation. A cytotoxicity failure normally sends you back to materials before irritation is worth starting.
What a pass tells you
That neither the polar nor the non-polar extract produced a local inflammatory response beyond the control under these conditions. The material passes when the difference between the mean test and control reaction scores is 1.0 or less.
What it does not tell you
Nothing about sensitization. Irritation is an immediate, non-immune response; sensitization is a delayed immune one, and a material can pass this and fail that. It also says nothing about cytotoxicity, genotoxicity or systemic effects — those are separate endpoints with separate tests.
Method
Testing per ISO 10993-23:2021. Two extracts are prepared — polar (saline) and non-polar (sesame or cottonseed oil) — at 5 mL per extract, using the ISO 10993-12 extraction ratios: 6 cm2/mL for material under 0.5 mm thick, 3 cm2/mL at 0.5 mm or thicker, or 0.1–0.2 g/mL where surface area is indeterminate. Each extract is injected intracutaneously at a minimum of two discrete dose portions, with the corresponding blank as control, and the sites are scored for erythema and oedema.
Choosing a source
Domestic and international laboratories are both ISO/IEC 17025 accredited and GLP certified. The choice affects price and turnaround, not the method or the standard — it is a sourcing decision, not a regulatory one.
Usually ordered alongside
Cytotoxicity and sensitization complete the surface-contact baseline under ISO 10993-1:2025. If you do not yet have a biological evaluation plan, that is the place to start — a BEP typically removes tests from a list rather than adding them.
