OECD 439 – Skin irritation testing

In vitro testing allows products to be tested for tolerability and efficacy before or instead of testing on a human subject. Tests on human subjects are unsuitable or even unable to address many issues or questions. Such testing is often associated with health or safety risks for the test subjects, hence, it is banned on ethical grounds or impossible in practice. This is why here at Dermatest we also use primary skin cells and 3D models of the skin when looking at complex issues.

Same testing method – new seal design

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Benefits of In vitro testing

using physical, histological and biochemical techniques, specific claims can be made regarding the effects of a product on biological processes in human skin.
3D models of the skin, grown from primary human cells, adequately reflect the natural properties of native human skin including all tyical skin layers as well as expression of characteristic markers.
comprehensive quantitative and qualitative assessment of various parameters is available
aspects which cannot be tested on human subjects, such as irritation tests, wound healing studiesinflammation or penetration/permeation can still be investigated
techniques can be adapted to the individual product and matter at hand, so that almost every aspect of tolerability and safety can be addressed
testing can often be done rapidly, as no human subjects are involved in the study

How we test OECD TG 439

For this test, 3D reconstructed human skin models are exposed to the test material for 1 hour. Afterwards models are rinsed and incubated for 24 hours. The next day, supernatant can be collected for analysis of cytokines (e.g. IL-1α, optionally). Viability is subsequently assessed using the MTT test (colorimetric assay). If remaining viability is > 50% the test material is non-irritant.

The Modified EpiDerm™ SIT allows discrimination to be made between irritants of category 2 and non-irritants. The test does not discriminate between non-mandatory subcategories of the UN GHS, i.e. it does not distinguish between GHS category 2 and category 3 irritants.

3D model of the skin

In order to provide you with the best possible testing methods for your product, our in vitro work is done using Phenion® skin models from Henkel® as well as EpiDermTM models from MatTek. The models are composed entirely of human skin cells (keratinocytes and fibroblasts). The design is modelled on human skin which it resembles in both anatomical and physiological properties. It consists of a fully differentiated epidermis and underlying dermis, containing connective tissue made from natural collagen synthesized by human fibroblasts. These highly specific human skin tissue models can be used to broaden our basic cosmetic research and assess the safety of raw materials and products. The investigations and tests which we perform on these models are as close as possible to native human skin and you get meaningful, marketable results.

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FAQ

How long does testing take at Dermatest, when does it start and when are the results available?

The start and duration of an application test is strongly dependent on the study design and availability of appropriate skin models. Usually it takes 3-4 weeks after product arrival to conduct the study and finalize the expert opinion.

How much product is needed for testing?

Unlike in vivo studies in vitro only needs a very small amount of a product (5 ml or 5 g) or substance. The amount of product for application ranges between 1- 100 µl or 1 – 50 mg depending on the study design. Frequency of use should be taken into account. We do not need a retention samples or spare samples.

What other documentation is needed for the testing to start?

Besides the product samples, the qualitative INCI names or composition of the test product is needed for all testing. As an order confirmation, we need the study protocol to be returned to us, signed (digital format is sufficient).

Who decides on the test design?

We offer various tests design which can always be adapted by the customer to suit the preferred test design or needs.

Does Dermatest only test cosmetic products?

No. In addition to cosmetic products, we also test consumer goods, medical devices and biocides for skin tolerability according to currently valid OECD testing guidelines or DIN EN ISO protocols.