Skin sensitivity study

The skin sensitivity study aims to assess the skin's reactivity to a given substance and to detect any potential allergen or irritant . This test is essential to ensure the safety of use of cosmetic and dermatological products, medical devices and natural ingredients before they are placed on the market.

Conducted according to ISO 10993-10 , the test measures the ability of a compound to provoke a sensitization-type immune response , generally delayed, after skin contact. It contributes to the biological characterization of materials and the validation of their safety.

Skin sensitivity studies are part of the overall toxicological evaluation strategy required by European regulations (Regulation (EC) No. 1223/2009 for cosmetics, ISO 10993 for medical devices).

Analytical methods and protocols used

Depending on the type of product and the purpose of the study, several approaches can be used:

• In vitro tests : performed on human cell cultures (keratinocytes, fibroblasts, reconstructed skin models).
  These tests measure the release of inflammatory markers (IL-8, TNF-α) or cell viability after exposure to the tested substance.
  Common methods
  Direct Peptide Reactivity Assay (DPRA) : evaluates chemical reactivity with skin peptides.
  KeratinoSens™ : measures the activation of cellular pathways involved in sensitization.
  h-CLAT (Human Cell Line Activation Test): analyzes the immune response of dendritic cells.

• Ex vivo or in vivo tests :
  Epicutaneous test (Patch Test) : controlled application of the substance on human skin (often on healthy volunteers or validated models).
  Local skin sensitization test (LLNA – Local Lymph Node Assay) , carried out on animal models according to international regulatory requirements (although gradually replaced by alternative in vitro methods).

These approaches are selected based on the type of matrix (ingredient, formulation, material) and applicable regulations .

Products and matrices concerned

The skin sensitivity study applies to a wide range of products:

• Finished cosmetic products : creams, serums, lotions, deodorants, hair coloring, sunscreens.
• Natural or synthetic ingredients : plant extracts, essential oils, preservatives, surfactants.
• Medical devices : dressings, implants, gloves, coating materials.
• Chemicals and technical formulations : polymers, solvents, inks, additives.

These analyses guarantee that the tested product does not cause redness, irritation or delayed allergic reaction , even with repeated use.

Industrial and regulatory applications

Skin sensitivity testing is essential for:

• Ensure regulatory compliance of cosmetic products and medical devices (ISO 10993-10, REACH, CLP).
• Assess skin tolerance when developing new ingredients.
• Establish proof of safety in safety dossiers (CPSR report for cosmetics).
• Reduce the use of animal testing through the integration of alternative in vitro tests validated by EURL ECVAM.

This study can be combined with other security and performance analyses, such as:

• The in vitro skin irritation test .
• Phototoxicity assessment for products exposed to light.

Interpretation of results

The results make it possible to determine:

• The level of risk of skin sensitization (low, moderate or high).
• conditions of use for the end user.
• Necessary formulation revisions ( elimination of a sensitizing ingredient, adjustment of pH or preservative system).

Test reports include a detailed scientific interpretation in accordance with ISO standards and OECD recommendations.

YesWeLab expertise

YesWeLab provides a network of ISO 17025 and COFRAC accredited partner laboratories , specializing in skin toxicology and biocompatibility testing .

Thanks to the YesWeLab digital platform , it is possible to submit your samples, track your tests and access your analytical reports online .

For any specific request, contact our scientific team to define a protocol adapted to your products and your regulatory requirements.