Why Are The Side Effects Of Chemo So Awful?

Chemotherapy is probably the most widely known form of cancer treatment out there. But a lot of its notoriety comes from the fact that it has some serious side effects, too.

Here’s why chemo is still considered a standard form of cancer treatment—even though the side effects can be so awful.

Why Do We Use Chemo To Treat Cancer?

Chemo is the most common form of cancer treatment. I usually describe it as medicine that treats cancer by killing fast-growing cells.

Cell growth gets halted by chemo in one of three ways, reports CureSearch for Children’s Cancer:

  1. The cell material needed to divide is not copied.
  2. Key enzymes or nutrients for the cell’s survival are replaced or eliminated.
  3. The cell is triggered to self-destruct.

Chemo is given to patients for several reasons, according to the National Cancer Institute:

  • To cure cancer
  • To lessen the likelihood of its return
  • To stop or slow its growth
  • To shrink tumors

Why Does Chemo Cause Side Effects?

Chemo drugs target any cells that grow rapidly and divide, reports the American Cancer Society. They don’t discriminate between cancer cells and healthy cells.

Healthy cells that divide quickly—such as bone marrow cells that form new blood cells or hair follicle cells—get damaged by chemo, which causes side effects.

But because new cells are constantly being made, some side effects like nausea or hair loss are short term and go away after treatment.

While cancer cells grow quickly, other cells of the body may also be growing quickly, especially in kids who haven’t finished going through puberty.

Chemo can damage these cells and prevent them from developing normally, which can cause late effects. This means effects aren’t experienced until years later when the child is older.

What Factors Determine How To Treat Childhood Cancer?

Right now, most patients who start chemo do so because we’re trying to kill the cancer cells. Unfortunately, other cells that are growing quickly are killed as well.

Some newer therapies target a specific abnormality in cancer cells. Those kinds of therapies tend to have fewer side effects. But for many kinds of cancer, these targeted therapies haven’t yet been developed.


What Are Some Chemo Side Effects?

There are different kinds of chemo drugs, and they all have their own potential side effects.

Hair loss, or alopecia, is probably one of the more noticeable physical side effects of chemo.

Mucositis—a painful irritation in the digestive tract—is another issue that chemo drugs can cause.

And bone marrow suppression is a big issue for a lot of cancer patients who are undergoing chemo.


Some chemo drugs can cause problems with how the heart pumps.

They can sometimes damage the liver or kidneys, too. Most of the time, those issues get better after treatment, but sometimes these side effects can be prolonged.

Chemo can sometimes cause learning difficulties as well.

Are Chemo Side Effects Different In Kids Vs. Adults?

With chemo, the biggest difference between kids and adults has to do with growth issues. Once you’re done growing, the side effects from chemotherapy won’t affect physical development as much.

I would say that, in general, kids tend to tolerate the side effects of chemo better than adults. This is usually because kids are healthier overall and haven’t had as many stresses on their bodies.

Most kids haven’t already struggled with illnesses that are common in adults—like heart disease, diabetes, or kidney problems—so their bodies bounce back more quickly.

So, as far as treating cancer is concerned, this means that kids can often tolerate stronger treatments without as many side effects.

Jill Beck
I've been an oncologist since 2010. With pediatric oncology, you get continuity of care with families—so you care for children when they're really sick and see them get better.

4 thoughts on “Why Are The Side Effects Of Chemo So Awful?

  1. If I’d known the damage chemo caused
    If I was fully informed of all the nasty side effects
    I would not have let my teenage daughter have it.
    She had surgery after chemo, so the tumour was removed. The consequences
    Of chemo we’re horrific,
    Weightloss down to 3 stone at the age of 12! Mucusitus that made her inside bleed… She cried to die!!… “Please mummy don’t let me wake up, I cannot do anymore”…
    Given the opportunity

    • Hi, Cheryl. You are absolutely right that chemo effects are horrible. I’m so sorry that your daughter—or any child—has to endure this. Thankfully, advancements are being made in cancer treatments, including proton therapy—which zeroes in with radiation on just the tumor, leaving healthy cells virtually untouched—and gene panel testing on tumors, bone marrow, or blood to determine which genetic markers are causing the cancer and then finding a treatment to target what’s causing the cells to change. Hopefully, treatments like these will become more widespread so that cancer patients won’t have to endure the awful side effects of chemo.

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