Biocidal products are preparations that contain active chemical substances and are used in a wide range - from disinfectants to pesticides to wood preservatives and antifouling paints. Depending on the intended use, these products can come into direct or indirect contact with human skin. Products such as hand sanitizers, surface cleaners and pesticides in particular can have a potentially irritating effect on the skin. Therefore, the Skin irritation test for biocidal products is a mandatory assessment both with regard to the safety of employees and the health of the end consumers.
Under the Biocide Regulation (BPR - 528/2012) of the European Union, the skin irritation potential of a biocidal product must be scientifically evaluated in order to allow it. In Turkey, similar requirements were adopted into national legislation by the Ministry of Health issued by the Ministry of Health. These evaluations must be carried out according to internationally recognized methods and according to the GLP principles (good laboratory practice).
The importance of skin irritation in biocidal products
Skin irritation is a local inflammatory reaction triggered by a substance contact with the skin and not due to the immune system. It is characterized by redness (erythema), swelling (edema), drought, cracks and sometimes necrosis. In the case of biocidal products, this risk is particularly critical in the following cases:
- Occupational Exposure: Employees working with pesticides, industrial disinfectants and wood preservatives are exposed to long-lasting and repeated skin contact.
- Consumer use: Household disinfectants, hand hygiene products and pest control sprays involve the risk of direct skin contact.
- Accidental contact: Acute exposures that may result from improper use or spilling of the products.
- Formulation ingredients: Ingredients such as surfactants, solvents, acids and bases can increase the risk of irritation.
The early determination of the skin irritation potential of biocidal products ensures that the product label contains appropriate warnings and the necessary protective measures are taken.
Methods for skin irritation tests
There are two internationally recognized basic approaches for assessing skin irritation in biocidal products: in-vivo (living 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)
The OECD Test Guide 404 defines the standard procedure for the acute skin irritation/corrosion test. With this method, the test substance is applied to the shaved skin of healthy rabbits. After 4 hours of contact time, the substance is removed and after 24, 48 and 72 hours, the skin reactions (erythema and edema) are evaluated on a scale from 0 to 4.
As part of the OECD TG 404, it is first evaluated whether the test substance is corrosive. If the substance is corrosive, there is no need for an irritation test. This is a step that prevents unnecessary animal testing.
2. In vitro skin irritation tests (OECD TG 439)
The modern approach gives priority to in vitro models to minimize the use of animals. OECD TG 439 is a validated test guide for in vitro skin irritation. This method uses three-dimensional tissue models (RHE) made from human skin cells.
- Epiderm™, Episkin™, Skinethic™: Commercially available, validated human skin equivalents.
- Test method: The test substance is applied to the tissue for 18-24 hours, then cell viability is measured by MTT test.
- Evaluation: A viability loss of more than 50% is classified as irritating.
In vitro methods are increasingly being used in the routine evaluation of biocidal products due to the renunciation of animal experiments, the rapid delivery of results and reproducibility.
3. Corrosion test (OECD TG 431 and TG 435)
The corrosion potential is a parameter that must be checked before the skin irritation is evaluated. Corrosive substances are determined using the OECD TG 431 (in-vitro skin corrosion test) and the OECD TG 435 (in vitro membrane barrier test). No irritation test is performed on substances that have been found to be corrosion.
Comparison of test methods for skin irritation in biocides
The following table summarizes the methods used in evaluating the skin irritation of biocidal products:
| Test method | Model | Application time | Evaluation criterion | Advantages |
|---|---|---|---|---|
| OECD TG 404 (in vivo) | Rabbit | 4 Hours contact + 72 hours observation | Erythem/edema score (0–4) | Clinical data, official recognition |
| OECD TG 439 (in vitro) | Human Skin Equivalent (RHE) | 18-24 Hours | Cell viability (MTT) | No animal experiments, fast, reproducible |
| OECD TG 431 (corrosive effect) | Human skin equivalent | 3 Min, 1 hour, 4 hours | Cell viability (<35% = corrosion) | Corrosion proof, no animal experiments |
| OECD TG 435 (membrane barrier) | Artificial membrane | For a short time | Membrane damage | Fast pre-screening, corrosion detection |
Skin irritation test under the BPR and national legislation
In the context of BPR (528/2012), a separate skin irritation assessment for the active substance and the finished product must be carried out for the approval of a biocidal product. These assessments must comply with the ECHA's guidelines and OECD testing guidelines.
In the approval dossier for the active ingredient, the skin irritation potential of the active ingredient itself is evaluated. In the product approval dossier, on the other hand, the skin irritation potential of the end product (active ingredient + auxiliary substances) is evaluated. In particular, the contribution of additives 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 with nano-test
For biocidal products manufacturers, skin irritation tests form the basis for the approval process as well as for the assessment of product safety. Nano-Test is a reliable solution partner for the biocide industry with its GLP-compliant analysis services in this area.
Nano-Test – Performance Description
NANO-TEST offers Skin Irritation Tests (Skin Irritation Test) for biocidal products. In our labs accredited to GLP and ISO/IEC 17025, in vivo (OECD TG 404) and in vitro (OECD TG 439, TG 431, TG 435) methods applied.
Our service portfolio:
- In vitro skin irritation test (OECD TG 439): Measurement of cell viability with RHE models, fast results without animal experiments.
- In vivo skin irritation test (OECD TG 404): Assessment of erythema and edema on the rabbit model, clinical data recognized by the supervisory authorities.
- Corrosion tests (OECD TG 431/435): Identification of corrosive substances, avoiding unnecessary irritation tests.
- BPR Compliant Reporting: Reports in full compliance with ECHA Guides and BPR attachments.
- Method Validation: Development and validation of methods specifically tailored to your product matrix.
All of our analyzes are presented as GLP-compliant reports that have an inspection permit and ensure data integrity (ALCOA+ principles).
Advantages of nano-test in the biocide skin irritation test:
- Competence in both methods: Both in-vivo and in-vitro irritation tests in one location.
- BPR compliance: Complete compliance with ECHA guidelines and BPR requirements.
- 3R Principles: In vitro methods are preferred whenever possible.
- Fast Results: In-vitro testing reporting within 3-5 working days.
- Specialist team: A team with experience in the fields of toxicology, biocidal law and analytical chemistry.
Skin irritation, which can be caused by biocidal products, poses a significant risk in both occupational exposure and consumer safety. The biocide skin irritation test is essential to assess this risk scientifically and the necessary Attach warnings to the product label. The selection of a method corresponding to the OECD inspection guidelines, the correct implementation and GLP-compliant reporting are prerequisites for approving your application for approval within the framework of the BPR.
With its GLP-accredited laboratory infrastructure, its specialist staff and well-founded knowledge of the current legal regulations, NANO-TEST comprehensively meets the requirements of manufacturers of biocidal products for skin irritation tests. Collaborate with Nano-Test to increase the safety of your products and accelerate market access.