Patient description: Fernandez is a 41 year man who is a professional soccer player. He came to the clinic with itchy foot. Physical exam revealed localized scaling and maceration between the third and fourth of his right toe. It became inflamed and sore, with mild fissuring. The dorsum and sole of the foot was unaffected. There is no pus or tearing in the affected area. He didn't use ant topical ointment on the lesion and has no positive history for any underlying disease such as DM. He smokes 15 cigarettes per day and drinks a beer per day. His family history is positive for hyperlipidemia in her mother and MI in her father. He is in relation with several partners and use condom during the intercourse. His physical exam and lab studies were normal otherwise. Tinea pedis infection confirmed as his diagnosis by the observation of segmented fungal hyphae during a microscopic KOH wet mount examination.

Clinical trial eligibility criteria: eligible ages (years): 9.0-999.0,  Seborrheic Dermatitis Participants legally competent to sign and give informed consent or (for adolescents) assent. 2. Males and females ages 9 years and older (inclusive) at the time of consent. 3. Females of childbearing potential (FOCBP) must have a negative serum pregnancy test at all study visits. 4. Post-menopausal women with spontaneous amenorrhea for at least 12 months or have undergone surgical sterilization. Cohort 1 only: 5. Subjects with seborrheic dermatitis who met for a prior ARQ-154 study, successfully completed a prior ARQ-154 study through final visit and are able to immediately enroll into this long-term safety study on the final visit of the previous ARQ-154 study. Cohort 2 subjects that have not participated in a prior ARQ-154 study: 6. Clinical diagnosis of seborrheic dermatitis of at least 3 months duration as determined by the Investigator. Stable disease for the past 4 weeks. 7. Seborrheic dermatitis of the scalp and/or face and/or trunk and/or intertriginous areas up to ≤20% BSA involvement. 8. An Investigator Global Assessment (IGA) of disease severity of at least Moderate ('3') at Day 1. 9. Overall Assessment of Erythema and Overall Assessment of Scaling scores of Moderate ('2') at Day 1. Cohort 2 subjects that have participated in a prior ARQ-154 study: 10. Clinical diagnosis of seborrheic dermatitis of at least 3 months duration as determined by the Investigator. 11. Seborrheic dermatitis of the scalp and/or face and/or trunk and/or intertriginous areas up to ≤20% BSA involvement  Planned excessive exposure of treated area(s) to either natural or artificial sunlight, tanning bed or other LED. 2. Subjects with any condition on the treatment area which, in the opinion of the Investigator, could confound efficacy measurements. 3. Subjects unable to apply investigational product to the scalp due to physical limitation. 4. Known allergies to excipients in ARQ-154 foam. 5. Subjects who cannot discontinue the use of strong P-450 cytochrome inhibitors e.g., indinavir, nelfinavir, ritonavir, clarithromycin, itraconazole, ketoconazole, nefazodone, saquinavir, suboxone and telithromycin during the study period. 6. Known or suspected severe renal insufficiency or moderate to severe hepatic disorders history of severe depression, suicidal ideation or C-SSRS indicative of suicidal ideation, whether lifetime or recent/recurrent. 7. Females who are pregnant, wishing to become pregnant during the study, or are breast-feeding. 8. Subjects with any serious medical condition or laboratory abnormality that would prevent study participation or place the subject at significant risk, as determined by the Investigator. 9. Subjects with a history of chronic alcohol or drugs abuse within 6 months of initiation of investigational product. 10. Current or a history of cancer within 5 years with the exception of fully treated skin basal cell carcinoma, cutaneous squamous cell carcinoma or carcinoma in situ of the cervix. 11. 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. 12. Subjects who are family members of the clinical study site, clinical study staff, or sponsor, or family members that live in the same household of enrolled subjects. Cohort 1 only: 13. Subjects who experienced an ARQ-154 treatment-related AE or a serious AE (SAE) that precluded further treatment with ARQ-154 foam in a prior ARQ-154 study. 14. Subjects that use any Excluded Medication and Treatments. Cohort 2 only: 15. Subjects who cannot discontinue treatment with therapies for the treatment of seborrheic dermatitis prior to the Day 1 visit and during the study according to Excluded Medications and Treatments. 16. Subjects with PHQ-8 >10 or modified PHQ-A >10 at Screening or Day 1. Cohort 2 subjects that have participated in a prior ARQ-154 study: 17. Subjects who experienced an ARQ-154 treatment-related AE or a serious AE (SAE) that precluded further treatment with ARQ-154 foam in a prior ARQ-154 study