What Is Radiation Sickness

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Radiation sickness, also known as acute radiation syndrome (ARS), is caused by exposure to ‘ionising radiation’. It can cause a range of symptoms and even lead to death within hours if there is large enough exposure. We will investigate what radiation is and how it can cause such terrible consequences. We will also explore the treatment methods and how radiation sickness can be avoided.1

What is radiation?

Radiation is the transfer of energy from one point to another through a particle or wave. We are exposed to many forms of radiation in our daily lives, which have no negative effects. These forms of radiation are known as non-ionising radiation, which includes visible light, UV light and radio waves. They have less energy and cannot damage our cells.3 The second type of radiation is known as ionising radiation. These high-energy radiation waves are able to remove electrons from cells when exposed for too long. This can cause cellular damage, which leads to many further complications depending on the extent of exposure. 2

Sources of radiation

We are exposed to forms of ionising radiation at all times. Most of the time, these come from natural sources, but we may also be exposed to man-made radiation in certain situations. 

Natural sources4

Our bodies have naturally adapted to the Earth’s ‘natural background radiation’. This is radiation that we are constantly exposed to but has little effect on us. There are 3 main types of natural radiation that we are exposed to:

Cosmic radiation

The sun and other stars in space constantly emit high-energy radiation that hits the Earth’s atmosphere. While most are absorbed and redirected, a small amount can pass through the atmosphere. This is what we experience on Earth as cosmic radiation. Different areas will have different levels of exposure as high altitude places will have higher levels of cosmic radiation, though this difference is very small.

Radon gas

Radon is a radioactive gas that is colourless and does not smell. It is produced by radioactive elements found in soil and rocks. Radon is an unreactive gas that rises through the soil and into the atmosphere without any changes. However, increases in exposure to radon can occur when radon gas becomes trapped in buildings and other structures, preventing it from passing into the atmosphere. It may pose a health risk at high levels.

Internal radiation

There are also radioactive elements within our bodies and the foods we eat. A famous example is bananas, which contain high levels of potassium-40, a radioactive isotope. These levels of radiation are small and have no negative effect on our health.

Man-made sources5

Many man-made sources are intentional and have a particular function in mind. However, excessive or frequent exposure can still lead to negative consequences:

Nuclear power plants

Nuclear power plants use a radioactive material known as Uranium to generate energy. Uranium produces large amounts of radiation, but these power plants are built to contain the radiation as safely as possible. Workers can only work for limited hours in a day to reduce the risk of overexposure, however this has very little impact on the general public. 

X-rays and CT scans6

This is radiation used for medical imaging. X-rays and CT scans use a form of ionising radiation to produce images of the inside of the body. The dose is safe for the patient and can be vital to providing care for the individual.


This is a method of using radiation to treat cancer. Radiation is able to kill cancerous cells and is an important part of modern cancer therapy. It can be difficult to target just cancer cells, leading to damage to normal nearby cells. This is why radiotherapy has many negative side effects.

How radiation affects the body7

As we mentioned before, ionising radiation can remove electrons from the atoms in our bodies. In doing so, it can cause changes in DNA, which is known as ‘mutations’. These mutations may not affect the cell. However, certain mutations can cause a cell to replicate without control and become ‘cancerous’. When chronically exposed to radiation (exposed to small doses of radiation too frequently) the most common result is developing cancer. However, if there is acute exposure (exposure to a large dose of radiation for a short amount of time) symptoms can be felt within hours and if it is not treated the individual may die within a few days.

The dose and duration that an individual is exposed to radiation can lead to different severity of symptoms. The type of radiation can also have an effect on how severe the damage can be.

Type of radiation

  • Alpha radiation - This form of ionising radiation can only pass through the width of a sheet of paper or a layer of skin. When exposed from the outside, it can cause damage to the skin, including an increased risk of developing skin cancer.
  • Beta radiation - This form of ionising radiation can be blocked by a few inches of plastic, so it usually results in burns if exposed externally. However, if it is swallowed, it can cause damage to internal organs.
  • Gamma radiation - This form of ionising radiation can pass through the body completely. It can cause damage to the skin as well as to internal organs, even if the exposure is external.

Dose and duration

Often, the dose of radiation exposure is closely related to the duration of exposure. The longer an individual has exposed to radiation, the larger the dose they receive. The dose of radiation is measured in units known as the grey (Gy). Mild radiation sickness can be caused by a dose between 1-6 Gy, however above 10 Gy will almost always result in death. The area of the body affected also results in different symptoms.

Symptoms of radiation sickness8

Early symptoms within the first few hours include:

  • Nausea and vomiting
  • Fatigue
  • Diarrhoea

Late symptoms can follow after days, weeks or even months:

  • Hair loss
  • Skin damage
  • Organ failure

Stages of radiation sickness8

Following exposure, there are 3 stages of radiation sickness that can follow:

Prodromal stage

This can begin from a few minutes to a few days after exposure. It presents with nausea, weakness or diarrhoea. At this stage, any damage to the blood vessels or the brain can cause death within days.

Latent stage

A few days after exposure, there will be no symptoms. This can last for days to months, depending on the areas of the body affected. If there is radiation damage to the gut and digestive system, the latent phase lasts for a few days. When there is damage to the blood, the latent phase can last up to 4 weeks.

Overt systemic illness stage

This is the final stage of radiation sickness. Depending on the organ system affected it is the stage that signals failure of the organs and often leads to death.

Diagnosing radiation sickness 9

When a patient is exposed to radiation, doctors take many steps to determine a diagnosis. The first thing to know is what source and duration of radiation the individual has been exposed to. The duration can be estimated using the time from exposure till the individual complains of nausea. Typically the shorter the time, the larger the dose. Frequent blood tests are also performed to measure levels of white blood cells and possible DNA damage in red blood cells. This can signify if there is damage to the bone marrow. A survey metre (Geiger counter) is used to determine the location where radiation particles are coming from as well as how much radiation is present. All of this information helps the doctor to find out how severe the illness is, how likely the patient will survive and which treatments should be used.

Treatment and management10

Treatment is often done based on the problems that the individual presents with, which can vary in different cases. In general, the first step in all patients is to thoroughly sterilise the body of radiation. This is done with water and a special solution that can clear radioactive particles. The individual is then given fluids and blood transfusions 'intravenously’ to maintain water and blood levels. Pain relief and antibiotics are given to reduce the risk of infections, as this can be fatal when there is a weak immune system. As a result of radiation, there is often a development of cancerous tumours, which are usually surgically removed. Chemotherapy and radiotherapy are avoided as they have too large of a negative effect on the patient. The outcome of treatment is largely related to the severity of exposure, if this is too large then treatment is unlikely to be successful. 


Although we are exposed to forms of radiation all the time, it will not have any effect on our day-to-day lives. Only in rare cases when we may be exposed to large amounts of ionising radiation can problems arise. Depending on the type and duration of exposure, the severity of radiation sickness can vary. There are many safety features and regulations on radiation exposure that will prevent overexposure, so it is very important to follow them. In doing so, you protect yourself from any negative effects of radiation.


  1. Acosta R, Warrington SJ. Radiation syndrome. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 [cited 2023 Oct 28]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK441931/
  2. What is Radiation? [Internet]. 2023 [cited 2023 Oct 28]. Available from: https://www.iaea.org/newscenter/news/what-is-radiation
  3. Non-ionising radiation [Internet]. [cited 2023 Oct 28]. Available from: https://www.hse.gov.uk/radiation/nonionising/index.htm#:~:text=Non%2Dionising%20radiation%20(NIR),frequencies%2C%20microwaves%20and%20radio%20frequencies
  4. NRC Web [Internet]. [cited 2023 Oct 28]. Natural background sources. Available from: https://www.nrc.gov/about-nrc/radiation/around-us/sources/nat-bg-sources.html
  5. Mirion [Internet]. [cited 2023 Oct 28]. Man-made sources of radiation. Available from: https://www.mirion.com/discover/knowledge-hub/articles/education/man-made-sources-of-radiation
  6. Medical uses of radiation [Internet]. [cited 2023 Oct 28]. Available from: https://energy.ec.europa.eu/topics/nuclear-energy/radiological-and-nuclear-technology-health/medical-uses-radiation_en
  7. Uptodate [Internet]. [cited 2023 Oct 28]. Available from: https://www.uptodate.com/contents/clinical-manifestations-evaluation-and-diagnosis-of-acute-radiation-exposure
  8. Cleveland Clinic [Internet]. [cited 2023 Oct 28]. Radiation sickness: what it is, symptoms & treatment. Available from: https://my.clevelandclinic.org/health/diseases/24328-radiation-sickness
  9. Radiation sickness - diagnosis and treatment - mayo clinic [Internet]. [cited 2023 Oct 28]. Available from: https://www.mayoclinic.org/diseases-conditions/radiation-sickness/diagnosis-treatment/drc-20377061#:~:text=Frequent%20blood%20tests%20over%20several,level%20of%20an%20absorbed%20dose.
  10. Radiation sickness - symptoms, causes, treatment | nord [Internet]. [cited 2023 Oct 28]. Available from: https://rarediseases.org/rare-diseases/radiation-sickness/

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This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Sameer Gonuguntla

MBBS, Imperial College London, UK

I am a medical student at Imperial College London with a keen interest in medical writing. I am interested in a wide range of fields in the world of health from medical technology to advances in surgical care. I have experience in academic writing and I wish to bring the complex world of research into a more digestible form for the public to have a better understanding of their health.

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