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 opinion of the Investigator (i.e., skin atrophy, ichthyosis, tinea infection, contact dermatitis).
- Cracked, crusted, oozing, or bleeding AD lesions in the designated lesional assessment area leaving insufficient skin that was adequate for TEWL assessments.
- Hypersensitivity to the active substance or to any of the excipients of dupilumab.
- Ocular disorder that in the opinion of the Investigator could adversely affect the individual's risk for study participation. Examples include -but are not limited to- individuals with a history of active cases of herpes keratitis; Sjogren's syndrome, keratoconjunctivitis sicca, or individuals with ocular conditions that require the use of ocular corticosteroids or cyclosporine.
- Healthy volunteers with a personal history of an atopic condition.
The above information was not intended to contain all considerations relevant to a participant's potential participation in a clinical trial.