Tolerance and Efficacy Open-label Study With RV4421B, in Various Populations With Atopic Dermatitis for 12 Weeks

Inclusion criteria: * Male or female, with any phototype according to Fitzpatrick classification aged: * Group 1 (infants group): from 3 months to 23 months old included * Group 2 (children group): from 24 months to 12 years old included * Group 3 (teenagers \& adults group): from 13 years old * Subject with a diagnosis of atopic dermatitis according to the U.K. Working Party's Diagnostic Criteria for Atopic Dermatitis (Williams HC, Burney PG, et al.). * Subject with studied areas (lesions and prevailing xerotic areas) limited up to 30% of the body surface area * Subject with mild to moderate Atopic Dermatitis Criteria related to treatments and/or products: • Topical corticosteroids treatments (following international treatment guidelines for each age sub-group and including investigator agreement) applied on AD lesions areas since 1 to 5 days before the inclusion and ongoing at the time of inclusion. \* \*The investigator will be authorized to adjust the treatment during the study. Exclusion criteria: Criteria related to the skin condition or the disease: * Infant with Atopic Dermatitis lesions or prevailing xerotic areas located on the diaper (groups 1 \& 2) * Subject with history of allergy or intolerance to any of the study product(s) ingredients or material used for the research * Subject having any other dermatologic condition than Atopic Dermatitis, or characteristics (like tattoo…) on the studied areas liable to interfere with the study assessments * Subject having a dermatological condition, an acute, chronic or progressive disease or history of disease liable to interfere with the study data or considered by the Investigator hazardous for the subject or incompatible with the study requirements * Knowledge of Acquired Immunodeficiency Syndrome or Infectious (acute or chronic) Criteria related to treatments and/or products: * Systemic biological immunosuppressive treatment established or modified within 12 weeks before the inclusion or planned to be started during the study * Phototherapy performed within 4 weeks before the inclusion visit or planned to be started during the study * Systemic non-biological immunosuppressive treatment established or modified within 4 weeks before the inclusion or ongoing or planned to be started during the study * Systemic corticosteroids treatment established or modified within 4 weeks before the inclusion or ongoing or planned to be started during the study * Systemic antibiotics for dermatological purposes treatment established or modified within 2 weeks before the inclusion or ongoing or planned to be started during the study * Systemic antihistaminic treatment established or modified within 2 weeks before the inclusion * Topical treatments (immunomodulators (TIMs), non-steroidal anti-inflammatory, antihistaminic, antibiotics for dermatological purposes or antiseptics) applied on studied areas within 1 week before the inclusion or ongoing or planned to be started during the study * Any other topical treatment or product applied on studied areas incompatible with the study or liable to interfere with the study assessments according to the investigator, in the weeks prior to the inclusion visit, ongoing or planned to be started during the study * Skin care product (including moisturizer) applied on the whole body between the evening before the visit and the inclusion. * Water and/or any cleansing product, applied on the whole body within 4 hours before the inclusion visit. If there is no studied area on the face, the subject is allowed to do a light face wash without time restriction (especially in the morning of the visit). * Subject who plans to modify his/her usual moisturizer (allowed outside studied areas) and/or care habits during the study Treatment of the mother if the subject of group 1 and 2 is breastfed: * Systemic biological immunosuppressive treatment established or modified within 12 weeks before the inclusion or planned to be started during the study * Systemic non-biological immunosuppressive treatment established or modified within 4 weeks before the inclusion or planned to be started during the study * Systemic corticosteroids established or modified within 2 weeks before the inclusion or planned to be started during the study * Systemic antihistaminic established or modified within 2 weeks before the inclusion * Systemic antibiotics for dermatological purposes established or modified within 1 week before the inclusion or planned to be started during the study