Safety evaluation for ingredients used in baby care products: Consideration of diaper rash

•Diaper rash can adversely impact barrier properties of skin, potentially increasing the absorption of chemicals.•We recommend assumptions to use in an exposure assessment regarding the extent, duration and severity of diaper rash.•The potential impact of diaper rash is illustrated for substances with varying degrees of absorption through healthy skin.•Where 100% dermal penetration is already assumed, the presence of diaper rash will not impact the assessment.•The assumptions made here are conservative and can be refined with additional data.

Diaper rash can adversely impact the barrier properties of skin, with potential implications for increased absorption of chemicals through the skin, and this should be accounted for in any exposure assessment used in the safety evaluation of consumer products used in the diaper (“nappy”) area. In the absence of a quantitative evaluation of the potential impact of diaper rash, a default assumption of 100% dermal penetration is often made for substances applied in the diaper area. We consider here the extent, duration and severity of diaper rash and make a recommendation for conservative assumptions to incorporate into exposure assessments. Using a time-weighted average, the potential impact of diaper rash is illustrated for substances that have varying degrees of absorption through healthy skin. Results confirm that for assessments that already assume dermal absorption of 50% or higher, there is no impact on the overall exposure assessment. For substances that have a very low degree of dermal penetration (1%) through healthy skin, the impact of rash is expected to be less-than four-fold. This can be refined with additional data as there are many examples of poorly absorbed compounds for which dermal penetration is still low even for compromised skin.