Chemotherapy is a common treatment for cancer. Depending on the type of cancer, different combinations of medications may be used as part of a chemotherapy treatment plan.

In general, chemotherapy medications work by attacking cells, or by preventing cells from growing and dividing. Cancer cells tend to grow and divide rapidly and uncontrollably. Many chemotherapy drugs are designed to target this type of rapid cell growth.

However, the body is made up of many types of cells, including healthy cells that naturally grow at a fast pace. Chemotherapy treatments can’t differentiate between cancer cells and healthy cells. That’s why chemotherapy harms or kills healthy cells, as well as cancer cells.

Many common side effects of chemotherapy are caused by the treatment’s impact on healthy cells. These side effects include anemia, a weakened immune system, hair loss, and nausea.

Although chemotherapy has the potential to cause side effects, not everyone reacts the same way to treatment. Knowing what’s happening in your body may help you to understand the side effects you experience during treatment.

Since chemotherapy drugs can’t tell the difference between cancer cells and healthy cells, the treatment affects many types of healthy cells, especially rapidly-dividing ones. This includes cells that help the body to function normally, such as blood cells.

Here are some of the main types of healthy cells that chemotherapy impacts:

  • red blood cells, white blood cells, and platelets
  • hair cells
  • cells that make up the mucus membranes of the mouth, throat, and digestive system

The damage that chemotherapy causes to these cells can lead to certain side effects. Here are five common side effects and why they occur.

Red blood cells provide your body with oxygen from the lungs. If chemotherapy harms red blood cells and lowers red blood cell counts, anemia occurs. The main symptoms of anemia are tiredness and weakness. It can also cause an irregular heartbeat, shortness of breath, dizziness, cold hands or feet, and headaches.

If you’re undergoing chemotherapy, your cancer care team will monitor your blood levels closely. Anemia can be treated with an iron-rich diet, iron supplements, or in some cases, blood transfusions.

White blood cells are a vital part of the body’s immune system. If chemotherapy significantly lowers white blood cell counts, a condition called neutropenia occurs. It becomes harder for the immune system to fight off viruses, bacteria, and other pathogens. This means the risk of infection is high.

It’s important for people getting chemotherapy to take steps to avoid getting sick. Wash your hands regularly, avoid crowded places, and stay away from people who may be sick. Careful food preparation and cooking can also reduce the risk of food poisoning.

Chemotherapy may also affect platelets, a component of the blood involved in clotting. A shortage of platelets means the body may have difficulty forming a blood clot in response to an injury. This can lead to excessive bleeding. However, if there are too many platelets in the blood, clots may form too easily, increasing the risk of heart attack or stroke.

Your cancer care team will keep track of your blood cell counts if you’re being treated with chemotherapy. Any suspected platelet issues can be treated with medication.

Hair cells are a type of rapidly dividing cell. Because many chemotherapies target rapidly dividing cells, hair loss is a common side effect of treatment.

However, not all types of chemotherapy cause hair loss. When chemotherapy does cause hair loss, it usually grows back after treatment stops. Some research has found that wearing a scalp cooling cap during chemotherapy infusions can help prevent hair loss.

Chemotherapy can affect the cells of the mucous membranes, causing side effects related to the digestive tract, including nausea and vomiting. Most people undergoing chemotherapy receive medication to prevent nausea. It’s easier to prevent nausea in advance than to treat it once it has started.

Another side effect is a condition called mucositis, which leads to sores in the mouth and throat. These sores can make everyday tasks like eating and drinking difficult. Good oral hygiene, regular dental exams, and not smoking may help prevent mouth sores. Prescription medication is also an option.

Although chemotherapy may cause a variety of side effects, most of them are short-term. They will likely go away or diminish after treatment has stopped.

Most side effects are also treatable. During chemotherapy, your cancer care team will monitor your health with regular testing. Medications, dietary changes, and complementary therapies are effective treatment options for a wide range of side effects.

The goal of chemotherapy depends on the type of cancer, its location, and a person’s unique circumstances. Based on the specific goal, there are three main categories of chemotherapy treatment:

  • Curative: The therapy attempts to destroy all cancer cells, so that a person is cancer-free.
  • Adjuvant or neoadjuvant: The therapy targets cancer cells remaining in the body after surgery or attempts to shrink cancerous growths prior to surgery.
  • Palliative: If the cancer cells can’t be eliminated, treatment may focus on relieving symptoms or slowing cancer growth.

Chemotherapy is often just one part of a larger treatment plan. It may be given with other treatments like radiation, surgery, or other medications.

Chemotherapy is a treatment that attempts to destroy or harm cancer cells. At the same time, it often impacts healthy cells, causing certain side effects. Most of these side effects are short-term and treatable. Your cancer care team can help you understand your specific chemotherapy plan, how it’s expected to work, and what side effects may occur.