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, which work to 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 has been affected, there are some precautions you can take to help avoid infection. These include:

  • avoiding people who have an infection
  • avoiding places where there is a risk of picking up an infection
  • avoiding crowds
  • checking with your doctor before you have any vaccines
  • maintaining a high standard of personal hygiene
  • protecting your central or PICC line (if you have one) 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 is very complex and has to work properly to protect us from harmful bacteria and other organisms in the environment, which may infect our bodies.

The immune system has three parts:

  • the skin and mucosal membranes
  • soluble proteins produced by the body, which are present in body fluids
  • specialised blood and lymph cells.

The skin and mucosal membranes

The skin and the lining of the body cavities that open to the outside, such as the gut and the reproductive tract, are protective barriers that prevent invasion by any harmful organisms.

The oil or sebum produced by the skin keeps it slightly acidic, which controls the growth of any organisms on the skin.

Cells in the lining of body cavities produce fluids such as saliva in the digestive system and mucus in the lungs, which provide a defence against harmful organisms.

The body also has its own natural and helpful organisms that prevent other more dangerous organisms from taking over.


Special proteins and chemicals are present in body secretions and fluids. If organisms do manage to enter the body, the proteins attack them in various ways, often by dissolving their protective outer layer.

Specialised blood and lymph cells

Specialised cells are produced by the bone marrow (the spongy cells in the middle of some of our bones) and the lymphatic system. The lymphatic system is a complex system made up of organs such as bone marrow, the thymus, the spleen and lymph nodes. Lymph nodes are found throughout the body and are connected by a network of tiny lymphatic vessels.

The lymphatic system
The lymphatic system

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Different types of white blood cells play varying roles in killing organisms that invade the body. They arrive at the site of damage or infection and destroy these organisms (known generally as antigens).

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

Cancer, its treatment and the immune system

Cancer and its treatment can affect the immune system in a number of ways. Some cancers, particularly lymphomas and leukaemias, may reduce the effectiveness of the body's natural immune defences. They do this by preventing the bone marrow from producing enough healthy white blood cells.


Surgery can make you more prone to infection because it involves making a break in the skin or mucous membranes, which are part of the body's natural defences. The likelihood of getting an infection is increased if an operation involves removing the spleen. The spleen is an important part of the immune system. Removing it will mean a person has permanently reduced immunity and may need to take antibiotics to protect themselves from infection (called prophylactic antibiotics).


This often has a mild and temporary effect on the immune system, which is unlikely to cause any problems except for people who have had radiotherapy to their whole body (total body irradiation). During total body irradiation, all the bone marrow in the body receives a dose of radiation that temporarily lowers the production of white blood cells, so the person will be at risk of infection for a while.


This can often have a major effect on the immune system and may reduce the body's defences against infection for some months, both during and after treatment. This is because chemotherapy reduces the number of white blood cells produced by the bone marrow. People having chemotherapy 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 known as the nadir, and it can vary slightly depending on the chemotherapy drug or combination of drugs used

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

Contact your doctor or the hospital straight away if:

  • you develop a high temperature, which may be over 37.5˚C (99.5˚F) or over 38˚C (100.4˚F) depending on the hospital’s policy – follow the advice that you have been given by your chemotherapy team
  • you suddenly feel unwell, even with a normal temperature.

These are signs of a possible infection and you may need to have antibiotic treatment, either as tablets or by drip (intravenous injection).

Avoiding infection

When your immunity is reduced for any reason, it's advisable to avoid other people who have sore throats, colds, flu, diarrhoea and vomiting, or other kinds of infection such as chickenpox. If you do come into contact with anyone who has an obvious infection, it's best to ask your hospital doctor or specialist nurse for advice as soon as possible. You may need to have medicines to prevent you from getting the infection.

It's important to go outside to get some exercise and fresh air during or after cancer treatment, but it's best to avoid crowds where possible. This includes avoiding using public transport, particularly during the rush hour, and crowded shopping centres where you may be mingling with people who have infections that are not obvious.

It's best to avoid swimming or using a public jacuzzi when your immunity is reduced. This is because there's a risk of picking up an infection from the water or in the changing room. Again, avoid crowds when doing other sports or social activities.

If you have pets or work with animals, you’ll need to be extra careful. It’s usually safe to pet or stroke animals as long as you wash your hands thoroughly afterwards. However, it's best to avoid handling any animal waste, such as litter trays or manure, as this can increase your chances of getting an infection.

If you aim to continue working during your treatment, it’s a good idea to talk to your employer or the human resources department. They should be able to offer you support and look at ways to help you avoid getting an infection. You may be able to work part-time or work from home during the times when your immunity is reduced.

While you have reduced immunity, you should be careful to avoid places where a mould/fungus called aspergillus is likely to be. It can grow in dead leaves, grain stores, compost piles or other decaying vegetation. Brick, mortar and cement dust may also contain this fungus.

It’s 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. But, depending on the type of cancer and treatment you’ve had, the vaccine may not give you quite as much protection against flu as in previous years. Generally, people with cancer are recommended to have the vaccine at least two weeks before starting treatment or between their chemotherapy cycles, and then yearly.

If you're planning a holiday abroad and need to get vaccinated before you go, check with your GP first. Some vaccines, known as live attenuated vaccines, should be avoided. These include measles, mumps, rubella and MMR, oral poliomyelitis liquid, oral typhoid, BCG and yellow fever.

If you have reduced immunity, your family and friends should also avoid having the oral typhoid vaccination.

Some vaccines, such as poliomyelitis, can be given in an inactivated form.


One of the most effective ways of avoiding infection is to maintain a high standard of personal hygiene. It's important to remember to always wash your hands when you have been to the toilet and before you are about to prepare or eat food.

It's also a good idea to take a daily shower or bath, if possible. However, it isn't advisable to share towels or flannels with other family members because of the possible risk of cross-infection.

Central lines and PICC lines

Some people receiving cancer treatment have central lines or PICC lines. These are long, hollow tubes made of silicone rubber. 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 pushed 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. If you have one, it is necessary to protect it from bacteria and possible damage. Your hospital or district nurse can give you advice about how to keep it clean. A transparent dressing is often used. It can be changed weekly and won't be affected by a shower or bath.

Mouth care

It’s possible to develop an infection in your mouth when your immunity is low. You’ll need to take extra care to keep it clean. Use a soft-bristle toothbrush that isn't too abrasive, as a hard one might cause the gums to bleed, which can increase the risk of infection.

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

Because of your risk of infection, it's 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, and will also flush out your kidneys and bladder, which prevents the build-up of debris where bacteria can grow. It's thought that drinks such as cranberry juice may also help reduce the risk of developing urinary infections.

For a variety of reasons, people often find it difficult to eat and drink when they have cancer. This may be due to the cancer itself or the side effects of treatment. For example, you may feel sick (nausea), or have taste changes that affect your appetite. However, it's important to try to eat a healthy and balanced diet as this will help maintain your immune system.

Some foods, especially shellfish, poultry and eggs, can have harmful bacteria in them. These bacteria are usually killed by heat or made less harmful by cold. It is advisable to ensure that all food is stored at the correct temperature and cooked thoroughly. It's also a good idea not to reheat food that has cooled, as this may allow bacteria to regrow.

You may be recommended to follow a 'clean' diet. This means avoiding salads that could be dirty and avoiding foods that could contain harmful bacteria. These include:

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

Advice on following a 'clean' diet will vary depending on the type of cancer you have and the treatment you are receiving. For example, the guidelines might be very strict if you have leukaemia and are having high doses of chemotherapy, or if you have had high-dose treatment with stem cell support. It's best to always check your diet with the hospital staff that are caring for you.

Your food needs to be carefully prepared so that infection can't pass from one food to another. All food should be used before its use by date, and care should be taken to keep raw and cooked foods apart. It's also important to keep clean foods away from potentially 'dirty' foods, such as those mentioned above.

Try to eat a varied diet as much as much possible. Also try to eat the recommended five helpings of fruit and vegetables every day. These contain essential vitamins and minerals, which should help keep you healthy. Wash fruit and vegetables thoroughly and peel before use. You may find it best to eat fruits that are easy to peel, such as bananas and oranges. You could also juice them and make fresh fruit juice to drink.