A Clinical Trial of the Administration of Light Therapy to Prevent Mouth Sores in Children With Cancer

The goal of this clinical trial is to learn if light therapy can prevent mouth sores in children with cancer. The main questions it aims to answer are: Is it reasonable and acceptable to provide light therapy for children with cancer? Does light therapy prevent mouth sores related to medical treatment? Researchers will compare children who do not receive light therapy to children who do receive light therapy during the clinical trial to see if light therapy helps to prevent mucositis. Participants will: * Complete a survey. * Have picture taken of their mouth to look for mouth sores. * Receive light therapy every day while admitted to the hospital on the cancer unit or while admitted to an alternate unit, and continue to receive light therapy in the home setting until they reach 8 days after the start of their chemotherapy cycle.

Inclusion Criteria: 1. Current and new diagnosis patients consented upon admission if deemed eligible 2. Ages 0-30 3. Admitted to CW oncology/BMT inpatient unit, PICU, or West 5 4. Chemotherapy regimen: Methotrexate ≥5 g/m2 (or ≥1 g/m2 if Trisomy 21) OR Anthracycline ≥60 mg/m2 5. Able to speak and understand English or Spanish Exclusion Criteria: 1. Patients admitted on BMT service 2. Patients currently experiencing mucositis with a CTCAE grade 4 oral mucositis or higher