Avoiding infection

The immune system protects the body from harmful bacteria and other organisms. Cancer and its treatment can weaken your immune system in a number of ways:

  • Some cancers, especially lymphomas and leukaemias, may stop the bone marrow from producing enough healthy white blood cells. These are the cells which fight off infections.
  • Chemotherapy and radiotherapy can reduce the number of white blood cells your bone marrow produces.
  • Surgery creates a break in the skin, which can make you more prone to infection.

If your immunity is affected, there are things you can do to help reduce the risk of getting an infection. These include:

  • Washing your hands regularly and having good personal hygiene.
  • Avoiding people with an infection, and crowds or public places where there is a risk of picking up an infection.
  • Checking with your doctor before you have any vaccines.
  • If you have one, protecting your central or PICC line from bacteria and damage.
  • Keeping your mouth clean.
  • Avoiding certain foods that may contain harmful bacteria.

The immune system

The immune system is the body's defence against bacteria, viruses and other foreign organisms, or harmful chemicals. It has to work properly to protect us from these things in the environment, which may cause infections.

The immune system has three parts:

  • the skin and mucous membranes
  • proteins produced by the body, which are in our body fluids
  • blood and lymph cells.

The skin and mucous membranes

The skin is important in protecting the body and our internal organs against infection. It also produces an oil which keeps the skin slightly acidic. This helps control the growth of any harmful organisms on your skin.

The mucous membranes also act as a protective barrier. They line areas of the body that are more open to germs. For example, the membranes of the mouth, nose, throat, digestive system, urethra (tube we pass urine out of) and vagina. They help stop harmful organisms and germs getting into your body. The cells of the mucous membrane also produce fluids, such as saliva in the digestive system, that help your body to destroy harmful organisms.

Your body also has its own natural and helpful organisms. These prevent more harmful organisms from taking over.


Special proteins and chemicals are present in the fluids your body produces. If organisms do get into your body, the proteins attack them in various ways. They often do this by helping dissolve the organisms.

Blood and lymph cells

Blood and lymph cells are produced by the bone marrow and the lymphatic system. The bone marrow is the spongy material in the middle of some of our bones. The lymphatic system is a system made up of organs, such as bone marrow, the thymus, the spleen, which contains white blood cells that fight infection and lymph nodes.

Lymph nodes are found throughout the body. They are sometimes called lymph glands. They are small and bean-shaped, and connected by a network of fine tubes called lymphatic vessels. Lymph nodes filter bacteria (germs) and disease from the fluid (lymph) that circulates around the lymphatic system. When you have an infection, the lymph nodes often swell as they fight it.

The lymphatic system
The lymphatic system

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Different types of white blood cells work to destroy organisms that get into the body. They travel through your blood or lymphatic vessels to the area of damage or infection. Then they destroy the harmful organisms.

How to avoid infection during chemotherapy

A slide show with tips for avoiding infection during chemotherapy. Chemotherapy reduces your immunity.

About our cancer information videos

How to avoid infection during chemotherapy

A slide show with tips for avoiding infection during chemotherapy. Chemotherapy reduces your immunity.

About our cancer information videos

How cancer and its treatment affects the immune system

Cancer and its treatment can affect the immune system in a number of ways.

The type of cancer you have

Some cancers, particularly lymphomas and leukaemias, can prevent the body's immune system from working properly. For example, they may do this by preventing the bone marrow from producing enough healthy white blood cells.


Surgery can make you more at risk of infection. This is because it makes a break in the skin or in the mucous membranes, which help protect the body from infection.

If the operation involves removing the spleen, infection is much more likely. The spleen is an important part of the immune system. It contains white blood cells that fight infection and gets rid of old red blood cells.

Having your spleen removed means that your immunity is permanently affected. Even though the spleen is only one part of your immune system, your doctor will advise you to take low-dose antibiotics for the rest of your life. This is to protect yourself from infection.


Radiotherapy usually only has a mild and temporary effect on the immune system. It’s unlikely to cause any problems.

This isn’t the same for people who are having radiotherapy to the whole body (total body irradiation). For this treatment all of the bone marrow receives a dose of radiation, so the person will be at risk of infection for some time afterwards. This type of radiotherapy is only occasionally used for people who are having a bone marrow transplant.


Chemotherapy reduces the number of white blood cells produced by the bone marrow. This can have a major effect on the immune system. It reduced your body's defenses against infection during and after treatment.

You are particularly at risk of picking up infections 7–14 days after the chemotherapy, when the level of white blood cells is at its lowest. This time is called the nadir. It can vary slightly depending on the chemotherapy drug or combination of drugs used.

Your number of white blood cells then increases steadily and usually returns to normal before your next cycle of chemotherapy. You will have your blood checked before you have more chemotherapy, to make sure the white cells are at a normal level. Your chemotherapy nurse will give you more information.

Infections can usually be effectively treated with antibiotics. If an infection is not treated quickly, it can be much more difficult to get it under control.

Contact the hospital straight away on the number you have been given if:

  • you develop a high temperature, which may be over 37.5˚C (99.5˚F) or 38˚C (100.4˚F) depending on the advice given by your chemotherapy team
  • you suddenly feel unwell, even with a normal temperature
  • you have symptoms of an infection – this can include feeling shaky, a sore throat, a cough, diarrhoea or needing to pass urine a lot.

These are signs of a possible infection. If you have an infection, you will need to have antibiotics either as tablets or by drip (intravenous injection).

Tips for avoiding infection

This information has some general tips to help you to reduce your risk of getting an infection when your immunity is reduced. Chemotherapy treatment is usually the most common reason for reduced immunity. Your doctor or specialist nurse will give you more advice.


One of the best ways to avoid infection is having good personal hygiene. You can do this by:

  • washing your hands regularly with soap and hot water
  • always washing your hands after you have been to the toilet
  • always washing your hands before you prepare or eat food
  • having a daily shower or bath – don’t share towels or flannels with anyone else, because there is a risk of picking up an infection.

Contact with others

  • Avoid people with sore throats, colds, flu, diarrhoea or vomiting or infections such as chickenpox. If you are in contact with anyone who has an obvious infection, ask your hospital doctor or specialist nurse for advice as soon as possible. You may need to take medicines to stop you from getting the infection.
  • Stay away from crowded places where there are likely to be people with infections. This means, avoiding public transport during rush hour and crowded shopping centres. This doesn’t mean you shouldn’t go out, but try to avoid the busiest times.
  • Avoid swimming or using a public Jacuzzi where there is a risk of picking up an infection from the water or in the changing room. If you are doing sports or social activities, try to go at quieter times.
  • If you have pets or work with animals, you need to be extra careful. It is usually safe to pet or stroke animals, as long as you wash your hands thoroughly afterwards. Avoid handling any animal waste, such as litter trays or manure.
  • If you aim to keep working during your treatment, talk to your employer or the HR department. They can give you support and look at making adjustments to help you avoid getting an infection. This could include working part-time or working from home when your immunity is reduced.
  • Avoid places where there is likely to be a mould/fungus called aspergillus. It can grow in dead leaves, grain stores, compost piles or other decaying vegetation. Aspergillus may also be found in building materials such as brick, mortar and cement dust, which means it might also be in places such as building sites. If you are worried about this, talk to your cancer specialist or nurse.


Vaccinations can reduce your chance of getting certain infections. It is always best to discuss any planned vaccinations with your consultant or specialist nurse.

It is safe to have a flu jab when your immunity is reduced. The flu jab is an inactivated vaccine, which means that it can't harm you. Depending on the type of cancer and treatment you have had, the vaccine may not give you the same protection against flu as in previous years.

If you have had chemotherapy, you may not be able to have some vaccinations. This is because your immune system may be weakened. You will need to avoid live vaccines. These include measles, mumps, rubella (MMR), oral typhoid, BCG, shingles and yellow fever.

If you are planning a holiday abroad and need to get vaccinated before you go, check with your GP first.

Central lines and PICC lines

Some people having cancer treatment have central lines or PICC lines. These are long, hollow tubes made of silicone. They are also called tunnelled central venous catheters.

A central line is inserted (tunnelled) under the skin of your chest into a vein. The tip of the tube sits in a large vein just above your heart. A PICC line is inserted into one of the large veins of the arm near the bend of your elbow. It is then threaded into the vein until the tip sits in a large vein just above your heart.

A central line or PICC line can stay in place for many months. You need to care for the line to protect it from bacteria and possible damage. Your nurse will show you how to do this and give you advice on looking after your line. You’ll be shown how to clean the line, which needs to be done once a week.

When you are at home, it is safe for you to have a shower or bath with your line in. Your nurse can give you waterproof covers to stop the line getting wet.

Mouth care

You can develop a mouth infection when your immunity is low. It is important to take extra care to keep your mouth clean. Use a soft-bristle toothbrush if your gums are sore. Check inside your mouth once a day for any signs of:

  • redness
  • swelling
  • ulcers
  • white patches
  • bleeding.

Your nurse at the hospital can show you how to do this.

Your doctor may prescribe antiseptic mouthwashes for you to use after meals and at night. Sometimes they may also prescribe antifungal tablets, mouthwashes or lozenges. These can help prevent infection from developing when they are used regularly.

Because of your risk of infection, it is important not to have any dental work done without discussing it with your cancer specialist first.

Eating and drinking

Drinking plenty of fluids can help prevent infection. Fluids help keep your mouth moist and healthy. Drinking plenty of fluids also flushes out your kidneys and bladder, which helps prevent bacteria from growing.

People may find it difficult to eat and drink for different reasons. This may be due to the side effects of treatment or the cancer itself. For example, you may feel sick or have taste changes that affect your appetite. But it's important to try to eat a healthy and balanced diet, as this helps your immune system.

Some foods can have harmful bacteria in them, especially foods such as shellfish, poultry and eggs. These bacteria are usually killed by heat or made less harmful by cold. Make sure your food is stored at the correct temperature and cooked thoroughly. Don’t reheat food that has cooled, as this may allow bacteria to grow again. All food should be used before its use by date. You should also keep raw and cooked foods apart.

If you have had high-dose treatment with stem cell support or if you have leukaemia and are having high doses of chemotherapy, you may given diet guidelines to follow. Your hospital can give you more information about this. They may give you a list of foods to avoid, which usually includes:

  • raw or lightly cooked eggs
  • shellfish
  • all types of pâté
  • soft cheeses
  • takeaway food
  • pre-wrapped sandwiches
  • cooked sliced meats
  • smoked fish
  • cream cakes.

Always wash salads, fruits and vegetables thoroughly. You may be asked to peel fruit.

If you have any more questions about avoiding infections, talk to your cancer specialist or nurse.