Acute Dermal Toxicity Tests Using OECD TG 402: Reliable Data on Skin Contact, an Ethical Approach
When assessing the potential risks of chemicals to human health, we cannot ignore the diversity of exposure routes.
Just as with inhalation and oral routes, skin contact is a critical route of exposure, particularly for industrial chemicals, pesticides, cosmetic ingredients, and cleaning products. This is precisely where the OECD TG 402 Acute Dermal Toxicity guideline comes into play. This guideline defines the internationally accepted standard protocol for evaluating the systemic toxic effects that a single exposure to a substance via intact skin may cause. Our laboratory applies this protocol under GLP (Good Laboratory Practice) principles, with the highest scientific rigor and ethical sensitivity.
OECD TG 402 Test Principle and Implementation Steps
The fundamental principle of OECD TG 402 is the application of a specific dose of the test substance to a shaved, intact skin surface on the test subject’s back and leaving it under a closed or semi-closed dressing for a specified period (typically 24 hours). The substance is then removed, and the test subjects are placed under intensive observation for at least 14 days. During this period, parameters such as behavioral changes, body weight fluctuations, clinical signs, and mortality are recorded. The ultimate goal is to determine the dermal LD50 value of the test substance and to classify the substance correctly according to GHS criteria.
The table below summarizes the key stages of the OECD TG 402 test procedure and the critical points to consider at each stage:
| Stage | Procedure | Critical Parameters |
|---|---|---|
| 1. Preparation | Shaving the application site, checking skin integrity | No skin lesions; the application site must cover at least 10% of the body surface area |
| 2. Dose Application | Uniform application of the test substance, covering with a dressing | Dose level (mg/kg), contact time (typically 24 hours), dressing type (closed/semi-closed) |
| 3. Termination of Exposure | Removal of the dressing, cleaning of residual material | Recording of signs of irritation or corrosion, gentle cleaning with water or an appropriate solvent |
| 4. Observation Period | At least 14 days of clinical observation | Mortality, changes in body weight, signs of systemic toxicity, behavioral abnormalities |
| 5. Necropsy | Macroscopic examination at the end of the observation period or in the event of mortality | Findings of target organ toxicity, local effects at the application site |
| 6. Reporting | LD50 calculation, GHS classification, data interpretation | Confidence interval, dose-response relationship, sex-related differences |
Why OECD TG 402? The Distinctive Role of Dermal Toxicity
Why do you need OECD TG 402? If your product’s use scenario involves direct or indirect skin contact, relying solely on oral toxicity data can be misleading. While some substances exhibit low toxicity when administered orally, they may exhibit much higher systemic toxicity via the dermal route due to different absorption kinetics through the skin. The opposite is also possible: a substance that is toxic when administered orally may not pose a dermal risk if it is not absorbed through the skin. Establishing this distinction through scientific data is both a legal requirement and an ethical responsibility in regulatory approval processes and in the preparation of Safety Data Sheets (SDS).
The table below compares OECD TG 402 with its supplementary guidelines and shows the role of each test within the regulatory context:
| OECD Guideline | Route of Exposure | Key Output | Scope | Contribution to GHS Classification |
|---|---|---|---|---|
| TG 402 | Dermal (Skin) | Dermal LD50, systemic effects | All chemicals, pesticides, and industrial products expected to come into contact with the skin | Acute Toxicity (Dermal) Categories 1–5 |
| TG 423 / 425 | Oral | Oral LD50, toxicity class | Substances with a risk of ingestion, active pharmaceutical ingredients | Acute Toxicity (Oral) Categories 1–5 |
| TG 403 / 436 | Inhalation | LC50, respiratory toxicity | Volatile substances, aerosols, gases, dusts | Acute Toxicity (Inhalation) Categories 1–5 |
The 3R Principles and Ethical Approach in Our Laboratory
In our laboratory, while conducting OECD TG 402 Acute Dermal Toxicity studies, we strictly adhere to the 3R principle (Replacement, Reduction, Refinement). Whenever possible, by pre-evaluating in vitro data on dermal absorption and skin corrosion/irritation, we work with you to determine whether in vivo testing is truly necessary. If testing is unavoidable, we optimize the protocol to yield the most reliable results with the fewest possible test subjects and apply refined techniques to minimize pain and stress throughout the experiment.
With our experienced team of toxicologists and state-of-the-art infrastructure, we provide clear, defensible, and internationally recognized data on your product’s dermal safety profile. For any questions or specific regulatory requirements, please contact us.
Frequently Asked Questions About OECD TG 402
| Question | Answer |
|---|---|
| For which types of substances is the TG 402 test suitable? | It is suitable for liquids, solids, paste-like substances, and formulated products (pesticides, cosmetics, cleaning products). For corrosive substances such as strong acids or bases, in vitro tests are primarily recommended. |
| How long does the test take? | The total process takes approximately 15–18 days, consisting of a 24-hour exposure period and an observation period of at least 14 days. Including reporting, the total duration may be 4–6 weeks. |
| Under which regulations are TG 402 results used? | They are used for classification, labeling, and the preparation of safety data sheets (SDS) under the EU REACH Regulation, the CLP Regulation, the U.S. EPA’s FIFRA and TSCA, and the Globally Harmonized System (GHS). |
| What data is required prior to testing? | The substance’s physicochemical properties (pH, solubility), available toxicity data, chemical structure-activity relationship (QSAR) analyses, and, if available, in vitro skin irritation/corrosion results are required for the preliminary assessment. |
Remember, the skin is not just a barrier—it is also a gateway. We’re here to help you understand what your product becomes as it passes through this gateway with our OECD TG 402 tests. Contact our GLP-certified laboratory, and let’s plan your acute dermal toxicity study using the most appropriate strategy.