Chemotherapy is a medical treatment that uses powerful chemicals to destroy cancer cells or slow their growth. When doctors discover cancer in someone's body, they might use chemotherapy as one way to fight it.

Cancer happens when cells in the body start growing out of control. Normal cells know when to stop dividing, but cancer cells keep multiplying and can spread to different parts of the body. Chemotherapy works by targeting cells that divide rapidly, which is exactly what cancer cells do. The medicines travel through the bloodstream to reach cancer cells almost anywhere in the body.

Unfortunately, chemotherapy also affects some healthy cells that naturally divide quickly, like those in hair follicles, which is why people receiving chemotherapy may lose their hair temporarily. It can also make patients feel tired or sick for a while. But once treatment ends, healthy cells usually recover and hair grows back.

Doctors have developed many different chemotherapy drugs over the past seventy years, and they continue improving these treatments to make them more effective with fewer side effects. While chemotherapy can be difficult, it has helped millions of people beat cancer and return to healthy lives.