Key Inclusion Criteria:  Participants legally competent to sign and give informed consent and, if appropriate, assent as required by local laws. Males and females ages 9 years and older at the time of consent. Clinical diagnosis of seborrheic dermatitis of at least 3 months duration at Screening as determined by the Investigator. Stable disease for the past 4 weeks. Seborrheic dermatitis up to 20% BSA involvement. Involvement may be of the scalp and/or face and/or trunk and/or intertriginous areas. An Investigator Global Assessment (IGA) disease severity of at least Moderate ('3') at Baseline. Overall Assessment of Erythema and Overall Assessment of Scaling scores of at least Moderate ('2') at Baseline. Females of childbearing potential (FOCBP) must have a negative serum pregnancy test at Screening (Visit 1) and a negative urine pregnancy test at Baseline (Visit 2). Females of non-childbearing potential must either be post-menopausal with spontaneous amenorrhea for at least 12 months or have undergone surgical sterilization. Subjects in good health as judged by the Investigator. Subjects are considered reliable and capable of adhering to the Protocol and visit schedule according to the Investigator judgment.  Key Exclusion Criteria:  Subjects who cannot discontinue treatment with therapies for the treatment of seborrheic dermatitis prior to the Baseline visit and during the study. Planned excessive exposure of treated area(s) to either natural or artificial sunlight, tanning bed or other LED. Previous treatment with ARQ-154 or ARQ-151. 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. Females who are pregnant, wishing to become pregnant during the study, or are breast-feeding. Subjects with a history of chronic alcohol or drug abuse within 6 months prior to Screening. Subjects, parent(s)/legal guardian(s) who are unable to communicate, read, or understand the local language(s). Subjects who are family members of the clinical study site, clinical study staff, or sponsor, or family members living in the same house of enrolled subjects.