Biocidal products are preparations that contain active chemical substances and are used in a wide range of applications—from disinfectants and pesticides to wood preservatives and antifouling paints. Depending on their intended use, these products may come into direct or indirect contact with human skin. In particular, products such as hand sanitizers, surface cleaners, and plant protection products can potentially cause skin irritation. Therefore, the skin irritation test for biocidal products is a mandatory assessment, both for the safety of employees and the health of end users.
Under the European Union’s Biocidal Products Regulation (BPR – 528/2012), the skin irritation potential of a biocidal product must be scientifically evaluated in order for it to be authorized. In Turkey, similar requirements were incorporated into national legislation through the Regulation on Biocidal Products issued by the Ministry of Health. These evaluations must be conducted using internationally recognized methods and in accordance with GLP (Good Laboratory Practice) principles.
The Significance of Skin Irritation in Biocidal Products
Skin irritation is a localized inflammatory reaction triggered by contact between a substance and the skin and not attributable to the immune system. It is characterized by redness (erythema), swelling (edema), dryness, cracks, and sometimes necrosis. For biocidal products, this risk is particularly critical in the following cases:
- Occupational Exposure: Employees who work with pesticides, industrial disinfectants, and wood preservatives are exposed to prolonged and repeated skin contact.
- Consumer Use: Household disinfectants, hand hygiene products, and pest control sprays pose a risk of direct skin contact.
- Accidental contact: Acute exposures that may result from improper use or spillage of the products.
- Formulation components: Components such as surfactants, solvents, acids, and bases can increase the risk of irritation.
Early identification of the skin irritation potential of biocidal products ensures that product labels include appropriate warnings and that the necessary protective measures are taken.
Methods for Skin Irritation Testing
There are two internationally recognized basic approaches for assessing skin irritation caused by biocidal products: in vivo (live animals) and in vitro (cell culture) methods. In accordance with the 3R principles (Replacement, Reduction, Refinement), in vitro methods are increasingly preferred.
1. In vivo skin irritation test (OECD TG 404)
OECD Test Guideline 404 defines the standard procedure for the acute skin irritation/corrosion test. In this method, the test substance is applied to the shaved skin of healthy rabbits. After a contact time of 4 hours, the substance is removed, and skin reactions (erythema and edema) are assessed on a scale of 0 to 4 at 24, 48, and 72 hours.
Under OECD TG 404, the first step is to assess whether the test substance is corrosive. If the substance is corrosive, there is no need to conduct an irritation test. This step helps prevent unnecessary animal testing.
2. In vitro skin irritation tests (OECD TG 439)
The modern approach prioritizes in vitro models to minimize the use of animals. OECD TG 439 is a validated test guideline for in vitro skin irritation. This method uses three-dimensional tissue models (Reconstructed Human Epidermis—RHE) derived from human skin cells.
- EpiDerm™, EpiSkin™, SkinEthic™: Commercially available, validated human skin equivalents.
- Test Procedure: The test substance is applied to the tissue for 18–24 hours, after which cell viability is measured using the MTT assay.
- Analysis: A loss of viability of more than 50% is considered problematic.
In vitro methods are increasingly being used in the routine evaluation of biocidal products because they do not involve animal testing, provide rapid results, and are reproducible.
3. Corrosion Test (OECD TG 431 and TG 435)
Corrosion potential is a parameter that must be assessed before evaluating skin irritation. Corrosive substances are identified using OECD TG 431 (in vitro skin corrosion test) and OECD TG 435 (in vitro membrane barrier test). For substances in which corrosion has been detected, no irritation test is performed.
Comparison of Test Methods for Skin Irritation in Biocides
The following table summarizes the methods used to assess skin irritation caused by biocidal products:
| Test Method | Model | Duration of Use | Evaluation criterion | Advantages |
|---|---|---|---|---|
| OECD TG 404 (In vivo) | Rabbits | 4 hours of contact + 72 hours of observation | Erythema/Edema Score (0–4) | Clinical data, regulatory approval |
| OECD TG 439 (In Vitro) | Human Skin Equivalent (RHE) | 18–24 hours | Cell Viability (MTT) | No animal testing, fast, reproducible |
| OECD TG 431 (Corrosiveness) | Human Skin Equivalent | 3 min., 1 hour, 4 hours | Zellviabilität (<35 % = Korrosion) | Corrosion testing, no animal testing |
| OECD TG 435 (Membrane Barrier) | Artificial Membrane | For a short time | Membrane damage | Rapid Pre-Screening, Corrosion Detection |
Skin irritation testing in accordance with the BPR and national regulations
Under the BPR (528/2012), a separate skin irritation assessment must be conducted for both the active ingredient and the finished product in order for a biocidal product to be authorized. These assessments must comply with the guidance documents published by ECHA and the OECD test guidelines.
The marketing authorization dossier for the active ingredient assesses the skin irritation potential of the active ingredient itself. The product marketing authorization dossier, on the other hand, assesses the skin irritation potential of the final product (active ingredient + excipients). In particular, the contribution of excipients such as surfactants, solvents, and pH regulators to the risk of irritation must be taken into account.
GLP-compliant skin irritation tests for biocidal products using Nano-Test
Skin irritation tests serve as the basis for manufacturers of biocidal products in both the authorization process and the assessment of product safety. With its GLP-compliant analytical services in this area, Nano-Test is a reliable solution partner for the biocidal industry.
Nano-Test – Statement of Work
Nano-Test offers skin irritation tests for biocidal products. In our laboratories, which are accredited according to GLP and ISO/IEC 17025, we use both in vivo (OECD TG 404) and in vitro (OECD TG 439, TG 431, TG 435) methods.
Our Service Portfolio:
- In vitro skin irritation test (OECD TG 439): Measurement of cell viability using RHE models, rapid results without animal testing.
- In vivo skin irritation test (OECD TG 404): Evaluation of erythema and edema in a rabbit model; clinical data recognized by regulatory authorities.
- Corrosion tests (OECD TG 431/435): Identification of corrosive substances; avoidance of unnecessary irritation tests.
- BPR-compliant reporting: Reports that are fully consistent with the ECHA guidance documents and the BPR annexes.
- Method Validation: Development and validation of methods specifically tailored to your product matrix.
All of our analyses are presented as GLP-compliant reports that have been approved for inspection and ensure data integrity (ALCOA+ principles).
Advantages of Nano-Test in the biocide skin irritation test:
- Expertise in both methods: Both in vivo and in vitro irritation tests conducted at a single location.
- BPR Compliance: Full compliance with the ECHA guidance documents and BPR requirements.
- 3R Principles: In vitro methods are preferred whenever possible.
- Fast results: Report on in vitro tests within 3–5 business days.
- Expert Team: A team with experience in the fields of toxicology, biocidal product regulation, and analytical chemistry.
Skin irritation caused by biocidal products poses a significant risk in terms of both occupational exposure and consumer safety. The biocidal skin irritation test is essential for scientifically assessing this risk and for including the necessary warning labels on product packaging. Selecting a method that complies with OECD test guidelines, performing the test correctly, and reporting in accordance with GLP are prerequisites for the approval of your application under the BPR.
With its GLP-accredited laboratory infrastructure, expert staff, and in-depth knowledge of current regulations, Nano-Test fully meets the requirements of biocidal product manufacturers for skin irritation testing. Partner with Nano-Test to enhance the safety of your products and accelerate market access.