Radiation sickness: causes, symptoms and care

The term is used in two ways, and it helps to separate them. Strictly, radiation sickness means acute radiation syndrome (ARS): an illness that follows exposure of much of the body to a very high dose of penetrating radiation within a short time. It is seen after serious accidents or emergencies, not after medical tests.

In everyday speech, people also use it for the queasiness, tiredness or bowel upset some experience during radiotherapy for cancer. That is a predictable, treatable side effect of a carefully planned dose to one part of the body, not the syndrome described by emergency planners. Both are covered here so that the two are not confused.

MedlinePlus explains that too much radiation can damage tissues by changing cell structure and damaging DNA. How much damage occurs depends on the type of radiation, the dose, how you were exposed, where the radiation concentrates in the body and how long it stays there, and how sensitive the body is.

The WHO says tissue damage depends on the absorbed dose, measured in grays, and the type of radiation and the sensitivity of the organs. Beyond certain thresholds radiation can impair tissue function and produce acute effects such as skin redness, hair loss, radiation burns or ARS, with more severe effects at higher doses and higher dose rates.

Dose rate matters. The WHO says that if the dose is low or delivered over a long time, the risk is substantially lower because there is more chance to repair the damage, though a long-term risk such as cataract or cancer remains and may appear years later.

MedlinePlus states that a fetus is the most vulnerable to radiation, and that infants, children, older adults, pregnant women and people with weakened immune systems are more vulnerable to health effects than healthy adults. The WHO says children and adolescents are significantly more sensitive than adults and gives thresholds for effects on the developing brain in pregnancy.

These points apply to high exposure. The WHO adds that most human-made population exposure comes from medical uses, mainly X-ray machines and CT scanners. A clinician considers the benefit of a scan against its very small dose, and you should say if you are or might be pregnant before any imaging.

MedlinePlus says symptoms include headache and diarrhoea, and they usually start within hours. These then go away and the person seems healthy for a while, but then becomes sick again. How soon this happens, which symptoms occur and how ill the person becomes depend on the amount of radiation received. In some cases ARS causes death in the following days or weeks.

Skin burns can occur with large exposures. The WHO describes skin redness, hair loss and radiation burns as acute effects. Because the pattern develops over hours to weeks, anyone with a known or suspected large exposure needs to be assessed even if they feel well at first.

• Headache, nausea and diarrhoea within hours of a large exposure

• A quiet phase when the person seems well, followed by renewed illness

• Skin redness or burns and hair loss in some people

• Increased risk of infection and dehydration as illness develops

• Severity that rises with the dose received

MedlinePlus advises that during a radiation emergency you should get inside a building to shelter, stay inside with windows and doors shut, and follow the advice of emergency responders and officials. In the UK, call 999 for anyone injured or unwell and follow instructions from the emergency services and public health authorities.

The WHO notes that external radioactive material on clothes or skin can often be removed by washing, while internal exposure stops when the radionuclide is eliminated or treated. Responders decide on decontamination, so do not try improvised remedies or take unprescribed tablets in response to news reports.

Before treatment, clinicians need to work out how much radiation the body absorbed. MedlinePlus says they ask about symptoms, do blood tests, may use a device that measures radiation, and try to learn the type of radiation, how far from the source you were and how long you were exposed.

Treatment focuses on reducing and treating infections, preventing dehydration and treating injuries and burns. Some people need treatments to help the bone marrow recover its function. If exposure involved certain types of radiation, a treatment that limits or removes contamination inside the body may be given, along with treatment of symptoms. Care is delivered in hospital under specialist teams.

Cancer Research UK says radiotherapy to the abdomen can make you feel or be sick, that this might last for a few weeks after treatment finishes, and that anti-sickness tablets from your radiotherapy doctor can usually control it. Diarrhoea is also normal during or after abdominal or pelvic radiotherapy, and tiredness is common.

These effects usually get better within a few weeks of finishing treatment, though some are longer-lasting. Report any side effect to your radiotherapy team, and do not stop treatment on your own. For diagnostic tests, MedlinePlus suggests asking about risks and benefits and whether a test without radiation would do the same job.