Side effects of chemotherapy in children and what parents watch for

The most common side effects in children are tiredness, nausea and vomiting, loss of appetite, a sore mouth, hair loss, constipation or loose stools, and a higher chance of infection. These happen because chemotherapy affects fast-growing cells, including those in the blood, gut, mouth and hair roots. Low blood counts are expected with most protocols: low white cells raise infection risk, low red cells cause tiredness and paleness, and low platelets can cause bruising or bleeding. Steroids, used in many childhood leukaemia protocols, can bring a big appetite, weight gain, mood swings and poor sleep. Some medicines, such as vincristine, can cause jaw pain, leg pain, constipation or a change in walking.

Children often cope better than parents fear. Many keep playing, eat what they can and bounce back between courses, and they usually recover from side effects faster than adults. Coping still varies. Younger children may become clingy or irritable, or slip back in sleep or toilet habits, while older children and teenagers may struggle more with hair loss, missing friends and losing control over their lives. Much of this can be eased. Anti-sickness medicines, mouth care, a dietitian's advice, gentle routines and play specialists all help. Letting children make small choices, such as which cup to use or which game to play, gives back some control. Tell the team early if a side effect is not settling.

Parents are usually the first to notice when something is wrong, so knowing what to watch for matters. Infection is the most serious risk, and it can become dangerous within hours in a child with low white cells. That is why the team will ask you to call straight away for any fever, or the temperature your child's team has told you to act on, even if your child seems otherwise fine. Also watch for bleeding, dehydration, severe pain, unusual sleepiness or breathing changes. Keep a working thermometer at home and the team's emergency number saved. This page describes common patterns only and cannot tell you which side effects your child's own medicines are likely to cause.

Low blood counts are expected

They drive infection, tiredness and bruising risks.

Children often bounce back

Side effects usually settle quickly between courses.

Fever is the key warning sign

Call the team straight away, day or night.

It cannot tell you which side effects your child will have, how severe they will be or how long they will last. That depends on the medicines in the protocol and on your child.

It also cannot assess a sick child. If you are worried, call the team rather than waiting.

Why fever matters so much

When white cells are low, a child cannot fight infection well, and an infection can become serious within hours. Fever may be the only early sign. That is why teams ask parents to call for any fever, or the temperature your child's team has told you to act on, even when the child seems cheerful.

Taking a temperature

Use a digital thermometer under the arm, or the method your team recommends for your child's age. Avoid taking temperatures in the bottom when counts are low. Ask the team before giving any fever medicine, because it can hide a fever that needs checking.

Anti-sickness medicines

Medicines such as ondansetron are often prescribed to prevent or ease sickness. Give them exactly as the team explains. If your child is still being sick, cannot keep tablets down or refuses fluids, call the team, because a different approach may be needed and dehydration can develop quickly in children.

Mouth care

A sore mouth makes eating and drinking painful. Brushing gently with a soft toothbrush, rinsing as advised and keeping lips moist all help. Tell the team about white patches, ulcers or pain that stops eating, because mouth infections are common during treatment and can be treated.

Steroid effects

Steroids can make children ravenously hungry, puffy in the face, moody, tearful or angry, and restless at night. These changes usually ease once the steroid part of the plan is over. Stay patient, offer healthy snacks, and tell the team if mood changes feel extreme or your child seems very distressed.

Nerve effects

Vincristine can cause jaw pain, leg aches, constipation, a drooping eyelid or clumsy walking. Children may trip more or struggle with buttons. Report these changes, because the team may need to review the plan, and a physiotherapist can help rebuild strength and balance at home.

Hair loss and appearance

Hair often starts to fall out within weeks of starting some medicines and usually grows back after treatment, sometimes with a different texture. Younger children often mind less than adults expect. Older children and teenagers may feel very self-conscious, so let them choose caps, scarves or haircuts.

Eating and weight

Taste changes, nausea and a sore mouth can make eating hard. Offer small, appealing portions, favourite safe foods and plenty of fluids. Avoid forcing food, which can create battles at mealtimes. A dietitian can suggest supplements or, if needed, tube feeding for a period to protect growth.

Bleeding and bruising

Low platelets can cause easy bruising, tiny red spots on the skin, nosebleeds or bleeding gums. Avoid rough play and contact sports when counts are low, use a soft toothbrush, and call the team about any bleeding that does not stop quickly or seems heavy.

How children cope emotionally

Children may show distress through tantrums, clinginess, withdrawal or going back to younger behaviours. These are normal reactions to a frightening experience. Keeping routines, allowing play, answering questions honestly and involving play specialists or counsellors helps children feel safer and more in control of what is happening.

Pain

Children do not always say they are in pain. Watch for crying, not wanting to move, guarding one part of the body or poor sleep. Pain from procedures can be reduced with numbing creams and sedation. Ask the team before giving any pain medicine at home.

Siblings and infection at home

Brothers and sisters can usually stay close, but good handwashing, not sharing cups and keeping unwell children apart help protect your child. Tell the team straight away if a sibling has chickenpox or measles, and ask the team which vaccines other family members should have to protect your child.

What to do next

Ask the team which side effects to expect with your child's medicines, save the emergency number, keep a thermometer and symptom diary at home, learn the warning signs above and call early whenever you are unsure.