Why can cancer chemotherapy damage healthy cells as well as cancer cells?

Chemotherapy drugs are designed to target and destroy cancer cells, primarily by preventing them from multiplying or by disrupting their cell division processes. However, because cancer cells are biologically similar to normal human cells, many chemotherapeutic agents—particularly cytotoxic drugs—cannot fully distinguish between the two.123

These drugs often affect any rapidly dividing cells in the body, not just those that are cancerous. Healthy tissues that naturally undergo frequent cell division, such as the bone marrow, the lining of the mouth, and other mucous membranes, are especially vulnerable to this interference.23

This lack of selectivity is the primary cause of common side effects, including hair loss, nausea, anemia, and a weakened immune system. While researchers continue to develop more precise targeted therapies that specifically attack molecular features unique to cancer cells, conventional chemotherapy remains a broad-acting treatment that inherently impacts healthy, actively multiplying cells.1243