Oral minoxidil is a commonly prescribed treatment for hair loss. The drug is also the active ingredient in over-the-counter Rogaine. The prescription treatment is known, however, to dilate blood vessels, and experts worry that this could increase the heart-related side effects of chemotherapy and lead to chest pain, shortness of breath, or fluid buildup. Now, a study in women with breast cancer suggests that low oral doses of minoxidil, taken during or after cancer treatment, appear to regrow hair in most patients and without causing any serious heart-related side effects that require additional therapies or hospitalization.