When your child starts pediatric cancer treatment, you will receive a stack of information about possible side effects. The list is long. The vocabulary is unfamiliar. You will not remember most of it.

This guide focuses on three of the most common side effects that affect daily life at home: mouth sores, neuropathy, and steroid effects. We chose these three because they show up in many treatment protocols, they are not always well-explained in the standard handouts, and they are the side effects parents tell us they wish they had understood sooner.

This is not a substitute for the conversations with your care team. It is the parent-friendly companion piece.

Mouth sores (mucositis)

What it is

Mucositis is inflammation and ulceration of the mucous membranes lining the mouth, throat, and sometimes the digestive tract. Chemotherapy is hard on rapidly dividing cells, which includes the cells that line the mouth. The result is mouth sores that can range from mildly uncomfortable to severely painful.

When it shows up

Usually 5 to 14 days after a chemo dose, peaking when blood counts are at their lowest (the nadir). It often resolves as counts recover.

What it looks like

Redness inside the mouth, especially on the gums and cheeks
Small ulcers or sores on the tongue, the inside of the cheek, or the back of the throat
Trouble eating, especially acidic, salty, or spicy foods
Difficulty swallowing in severe cases
Cracked or sore lips

What helps

Soft, bland foods (mashed potatoes, yogurt, smoothies, oatmeal, soft pasta, scrambled eggs)
Cold foods (popsicles, ice cream, frozen yogurt). Cold can be soothing.
Avoid acidic foods (citrus, tomatoes), salty foods, spicy foods, and crunchy foods
Soft toothbrush. Sometimes a sponge brush. Always with gentle pressure.
Salt-water or baking-soda rinses (your care team will tell you the recipe)
Magic mouthwash (a compounded oral rinse with multiple ingredients, prescribed by your team)
Lots of fluids
Sometimes pain medication (only as directed by your team)

When to call the care team

Severe sores that prevent eating or drinking
Bleeding from the mouth
Fever (per your team's threshold)
Signs of dehydration

Neuropathy (chemotherapy-induced peripheral neuropathy)

What it is

Peripheral neuropathy is nerve damage that causes tingling, numbness, weakness, or pain, usually in the hands and feet. Certain chemotherapies, especially the vinca alkaloids (vincristine, vinblastine), commonly used in leukemia and lymphoma treatment, can cause neuropathy.

What it looks like

Tingling or pins-and-needles in fingers or toes
Numbness in hands or feet
Weakness, especially in the hands (your child may struggle with fine motor tasks like buttoning a shirt)
Cramping in the feet or calves
Difficulty with balance or coordination
Constipation (vincristine can affect the nerves that control the digestive system)
Jaw pain, in some cases

What helps

Reporting symptoms to your care team. They may adjust dosing if symptoms are significant.
Soft, supportive shoes and socks. Avoid tight footwear.
Gentle stretching and movement, if cleared by the team
Avoid extreme temperatures (very hot baths, very cold ice packs) that can intensify nerve symptoms
Constipation prevention (your team may recommend stool softeners or laxatives during certain chemo phases)
Physical therapy or occupational therapy, if recommended by the team
Patience. Most neuropathy improves after treatment ends, sometimes slowly.

When to call the care team

New numbness or weakness
Significant difficulty walking
Severe constipation or no bowel movement for several days
Severe pain
Jaw pain or facial drooping

Steroids (corticosteroids like prednisone and dexamethasone)

What they are

Steroids are part of many pediatric cancer protocols, particularly for leukemia and lymphoma. They are powerful anti-cancer drugs, not just anti-inflammatory medications. Steroids work alongside chemotherapy to fight the cancer.

They also have significant side effects, especially behavioral and emotional ones, that families need to be prepared for.

What it looks like

Increased appetite (sometimes dramatic; sometimes only for specific foods)
Mood changes: irritability, anger, sadness, anxiety, sometimes rapid switching between moods
Sleep disruption
Restlessness or hyperactivity
Weight gain
Facial swelling ("moon face") and abdominal swelling
Acne or skin changes
High blood sugar (some children require monitoring or temporary insulin)
Increased thirst and urination
Muscle weakness, especially in the hips and thighs
Heightened risk of infection (steroids suppress immune function)

What helps

Have favorite foods stocked. Steroid hunger is real. Plan ahead.
Be patient with mood swings. They are pharmacologic, not personal. Your child is not being difficult on purpose.
Build in extra rest, quiet time, and physical comfort
Soften the schedule during steroid weeks if possible. Cancel non-essential commitments.
Use simple, predictable routines. Predictability soothes a steroid-dysregulated child.
Let go of normal behavioral expectations. "Use your words" does not always work during a steroid week.
Communicate with school and caregivers. They need a heads up.
Take care of yourself. Steroid weeks are exhausting for parents.

When to call the care team

Concerning behavioral changes (severe rage, persistent dark mood, self-harm thoughts in older children)
Signs of high blood sugar (extreme thirst, frequent urination, fatigue, weight loss)
Signs of infection (fever, even mild; concerning skin changes)
Severe sleep disruption
Anything else your gut says to call about

A note about steroid weeks

Steroid weeks are some of the hardest of pediatric cancer parenting. The child you love is, temporarily, a more dysregulated version of themselves. The parent's job is to absorb that dysregulation with as much grace as you can.

Some things that have helped families we know:

Pre-stock favorite foods (one cancer mom we know calls it the "steroid pantry")
Take turns. If you have a partner, tag-team the steroid days.
Plan low-key activities. Backyard time. Quiet TV time. Drives. Anything that is not a high-stimulation outing.
Lower the bar for everything. Skip the bath. Order delivery. Watch the same movie twice. The goal is to get through the week.
Tell yourself, "this is the drug, not my child." Repeat.
Remind your child the same thing, age-appropriately: "You are having a hard time today. Some of that is the medicine. Mommy is right here."

A note for the parent reading this

Side effects are normal. They are predictable. They are managed by your care team and softened by what you do at home.

If a side effect feels scary, call your team. If you have a question about whether something is normal, call your team. There are no silly questions. They want to hear from you.

Dina
Mom of Max | Founder, Maxwell’s Toy Shoppe
Childhood Cancer Advocate 💛

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