Inclusion Criteria:  Informed consent by parent(s) or legal guardian as required by local laws. Males and females, ages 2 to 5 years old at time of signing Informed Consent (Screening) and at Baseline (Day 1). Diagnosed with atopic dermatitis for at least 6 weeks, as determined by the Investigator. Stable disease for the past 4 weeks with no significant flares in atopic dermatitis before screening. In good health as judged by the Investigator. Subjects considered reliable and capable of adhering to the Protocol and visit schedule, according to the judgment of the Investigator.  Exclusion Criteria:  Subjects with any serious medical condition or clinically significant abnormality that would prevent study participation or place the subject at significant risk, as judged by the Investigator Has unstable AD or any consistent requirement for high potency topical steroids. Subjects who are unwilling to refrain from prolonged sun exposure for 4 weeks prior to Baseline/Day 1 and during the study. Previous treatment with ARQ-151. Parent(s)/legal guardian(s) who are unable to communicate, read, or understand the local language(s). Subjects who are unable to communicate, read or understand the local language, or who display another condition, which in the Investigator's opinion, makes them unsuitable for clinical study participation. Subjects who are family members of the clinical study site, clinical study staff, or sponsor, or family members of enrolled (in other studies of ARQ-151) subjects living in the same house.