OECD 406, also known as the Skin Sensitization test, is used to identify substances with the potential to cause allergic contact dermatitis or skin sensitization in humans. The study design follows the current OECD Test Guideline 406 entitled “Skin Sensitization” and is typically performed in accordance with Good Laboratory Practice regulations. This test is part of the Acute Toxicity Six-Pack tests
Test animals are initially exposed to the test chemical by intradermal injection and/or epidermal application (induction exposure). Following a rest period of 10 to 14 days (induction period), during which an immune response may develop, the animals are exposed to a challenge dose. The extent and degree of skin reaction to the challenge exposure in the test animals is compared with that demonstrated by control animals which undergo sham treatment during induction and receive the challenge exposure.
The test can be performed in one of two ways:
- The Guinea Pig Maximisation / Guinea Pig Maximization Test (GPMT) Method
- The Buehler Test Method
Guinea Pig Maximization Test Method (GPMT)
The GPMT involves induction of sensitization by use of an adjuvant, typically Freund’s complete adjuvant. It involves three exposure phases – intradermal injection, topical application, and challenge (topical application). At least 10 animals are used in the treatment group and 5 in the control group. If results are ambiguous, testing in additional animals (at least 20 test and 10 control) is recommended
The Buehler Test Method
The Buehler test method does not involve the use of an adjuvant. Test animals are repeatedly exposed to the test substance by topical application through an induction and a challenge phase. A minimum of 20 animals are used in the treatment group and at least 10 animals are used in the control group.
Typically 80 grams of test article are required for either the Guinea Pig Maximization (GPMT) or the Buehler Test Method. This test is performed in compliance with Good Laboratory Practice Regulations.
How to Choose between the GPMT or the Buehler Test Method
The GPMT is considered a more severe or rigorous test compared to the Buehler method due to the use of an adjuvant for induction. Adjuvants are known to enhance skin sensitization. As such, the GPMT is generally more sensitive in detecting skin sensitizers compared to the Buehler test. However, the Buehler test provides advantages of an allergic contact dermatitis test without use of an adjuvant.