Statement: Women of any age can participate in the primary trial, but only adults can be eligible for the secondary trial.
Primary_evidence: Inclusion Criteria:   Women at any age with early stage breast cancer (stage I-II) and American Society of Anesthesiologists (ASA) score of I-II. Exclusion Criteria:   Ductal carcinoma in situ (DCIS; stage 0 cancer),   Advanced or distant metastatic stage,   Receiving any neoadjuvant therapy,   History of receiving any antibiotics within prior 3 months,   History of immunodeficiency,   Having a remote infection,   History of reaction to study antibiotics,   Denial of signing the consent form.
Secondary_evidence: Inclusion Criteria:   Age 18 years   Stage 1-4 invasive breast cancer that is histologically confirmed at MSKCC   Status post mastectomy with axillary exploration (sentinel node biopsy and/or axillary lymph node dissection) to receive PMRT   ECOG Performance Status of 0 or 1 Exclusion Criteria:   Male   Patients with clinical evidence of gross disease   Patients who are pregnant or breastfeeding   Prior radiation therapy to the ipsilateral chest wall or thorax   Patients requiring a chest wall boost   Concurrent chemotherapy (biologic agents are allowed)   Psychiatric illness that would prevent the patient from giving informed consent   Inability or unwillingness to comply with skin care instructions and follow-up   Allergy to either Eucerin or MF   Residual grade >1 skin toxicity, cellulitis, or incompletely healed wound(s) at intended site of study drug application at the time of the start of RT   Medical condition such as uncontrolled infection (including HIV), uncontrolled diabetes mellitus, or connective tissue diseases (lupus, systemic sclerosis, or other collagen vascular diseases)   Treatment with palliative or pre-operative radiation