Breast Cancer Treatment: Things to Avoid While On Chemotherapy There are a few things to avoid while on chemotherapy. First, avoid drinking alcohol. Alcohol can interact with chemotherapy drugs and make them less effective. It can also cause side effects like nausea and vomiting. Second, avoid exposure to sunlight or bright light. Chemotherapy can make your skin sensitive to light, so it’s best to stay out of the sun. Third, avoid strenuous activity. Chemotherapy can make you feel tired and weak, so it’s best to take it easy. Lastly, avoid contact with people who are sick. Chemotherapy can weaken your immune system, so it’s best to avoid contact with people who are sick. Before participating in an activity, it is best to talk to your breast cancer treatment doctor.