The purpose of this study is to see if the investigators can prevent or reduce the severity of the Cetuximab-related acne rash. Two different topical agents will be applied to the skin. One topical agent is the dapsone gel and the other is a skin moisturizer. Dapsone gel is an FDA approved medication that you apply to the face. It is commonly used to treat acne. Skin moisturizers are recommended to patients who receive Cetuximab treatment. In addition to these topical agents they will be given a pill to take once a day. This pill has already been shown to help fight rashes from Cetuximab.

Inclusion Criteria:

• Patients 18 years or older with underlying diagnosis of metastatic colorectal cancer or head and neck squamous cell carcinoma including newly diagnosed patient
• Patients must provide written informed consent to participate in the study
• Anticipated initiation of cetuximab treatment with or without additional chemotherapy.
• Able to self-administer topical interventions or provide for another person to apply the topical interventions

Exclusion Criteria:

• Females of childbearing potential who are pregnant or nursing
• Patients with allergy, hypersensitivity or other contraindication to dapsone, sulfa antibiotics, or excipients of the dapsone gel product
• Patients with pre-existing dermatologic condition affecting the face and chest that would impair assessment of papulopustular rash including dense and/or long facial hair (per investigator discretion)
• Patients currently using prescription and/or over-the-counter topical medications to the face and/or chest who are unwilling to discontinue use during the trial intervention period (day 0 ± 2 days through day 28 ± 2 days)
• Previous or concurrent radiation therapy to head, neck, and chest (i.e. application sites only)
• Previous therapy with cetuximab within 6 months of consent