Dupilumab-PEdiatric Skin Barrier Function and LIpidomics STudy in Patients With Atopic Dermatitis

Inclusion criteria : * Participant must be between \>=6 to \<12 years of age (inclusive), at the time of signing the informed consent * 15 kg \<= body weight \<60 kg. Atopic dermatitis participants: * Male or female pediatric participants. * Participants with AD diagnosis according to Hanifin and Rajka criteria at least 1 year before screening. * Investigator Global Assessment (IGA) score of \>=3 (for US participants) or IGA \>=4 (for EU participants) at screening (on the 0-4 scale) depending on approved label indication in the country. * Participants with moderate to severe AD those were eligible to be treated with dupilumab according to product label. * Participants with AD must have had active lesions on the upper limbs or lower limbs (including trunk, if needed), with severity for lesion erythema or edema/papulation \>=2 at screening on the 0-3 scale of the Individual Signs Score. * Participants should have had a non-lesional (normal looking) skin area 4 centimeter (cm) from the edge of the lesional area. If unable to identify non-lesional skin 4 cm from the lesional area, it was acceptable to identify normal looking skin as close to the lesion as possible. Healthy volunteers: \- Age and gender matched (match on age ±2 years) to a selected AD participant by study site. Exclusion criteria: * Previous treatment with dupilumab within 6 months prior to screening. * Skin conditions other than AD that can confound assessments in the area of TEWL assessments in the opinio…