Skin sensitisation, vehicle effects and the local lymph node assay

Area of Science:

• Dermatology
• Toxicology
• Chemical Risk Assessment

Background:

• Accurate risk assessment for allergic contact dermatitis requires identifying skin sensitizers and their potency.
• The local lymph node assay (LLNA) provides quantitative potency assessment via EC3 values.
• Vehicle matrices can influence the evaluation of chemical sensitizers.

Purpose of the Study:

• To review the impact of vehicle matrices on the assessment of chemical skin sensitizers.
• To detail potential mechanisms of vehicle effects.
• To evaluate the significance of vehicle effects on hazard identification and potency estimation.

Main Methods:

• Review of existing knowledge on vehicle effects in skin sensitization testing.
• Analysis of data using the local lymph node assay (LLNA) as an example.
• Examination of potential mechanisms for vehicle-induced alterations in sensitization potential.

Main Results:

• Vehicles have minimal impact on hazard identification accuracy for skin sensitizers.
• Vehicle matrices can cause significant (over 10-fold) changes in the estimated potency of certain allergens.
• Predicting vehicle effects on potency without direct testing is currently not feasible.

Conclusions:

• Product formulation testing is not essential for hazard identification of skin sensitizers.
• Accurate potency estimation, vital for risk assessment, is significantly affected by vehicle matrices.
• Direct testing, such as LLNA EC3 estimation, is essential for determining vehicle-specific potency impacts.