Acute radiation syndrome follows a whole-body dose delivered in a short time and runs in stages: early nausea and vomiting, a quiet period that can look like recovery, then illness from bone marrow and gut damage, ending in recovery or death. The higher the dose, the earlier vomiting begins and the shorter the quiet period, and at the highest doses the prognosis is poor regardless of what care is available.
Part of Radiation Safety
Acute radiation syndrome is the illness caused by a large dose of penetrating radiation to much of the body within a short period, as opposed to cancer risk from lower or slower exposure.
Early Vomiting Means A Higher Dose, Not A Diagnosis
The parent article, Nuclear Safety, says vomiting within 1 hour of exposure indicates a potentially lethal dose and within 10 minutes indicates an almost certainly lethal one. Its own table is more graded: nausea and vomiting within hours at the lower bands, within minutes in the 4-6 sievert band and immediately above that. The two do not line up exactly, and this guide does not reconcile them with a new figure. The safer reading is the consistent one: the earlier the vomiting, the higher the dose, so earlier is more serious. Vomiting has other causes (fear, food poisoning), so it is a triage hint, not a measurement.
The Illness Moves Through Stages
The staging is standard medical teaching, recalled rather than taken from the parent article:
- Prodromal stage. Nausea, vomiting and fatigue within hours of the dose.
- Latent stage. The patient feels better. The marrow and gut damage is still developing. Higher doses shorten this stage.
- Manifest illness. What appears depends on the dose. The parent table lists falling blood-cell counts over weeks, hair loss, haemorrhage, infection risk, then at higher bands gut-tract destruction and, at the top band, cardiovascular collapse.
- Recovery or death.
The parent article notes the patient becomes severely immunocompromised after 1-3 weeks, so any wound can become fatal. That timing matters: a patient who looks well on day three may not be well.
What The Parent Table Says About Prognosis
The parent’s table gives rough outcomes by band: full recovery at the lowest, recovery likely with supportive care at 1-2 Sv, 50 percent mortality without medical care at 2-4 Sv, 50-90 percent mortality even with care at 4-6 Sv, near 100 percent fatal within 2 weeks at 6-10 Sv, and death within hours to days above that. The full table, with its unit caveats and disagreements, is in Dose Thresholds. This guide does not add to those figures.
What Care Exists
Supportive care, meaning fluids, hygiene, infection control, nutrition and comfort, is all a settlement can offer; see Treatment Protocols. Hospital measures exist (blood-product support, growth factors, antimicrobials, in some cases marrow transplant) but are not field options.
Common Mistakes
- Judging severity by how the patient looks in the latent stage.
- Isolating the patient to protect others. An irradiated patient is not radioactive. Isolation, if used, protects the patient from infection; see Contamination vs Irradiation.
- Promising recovery or predicting death on the basis of one sign.
Safety
A person with these symptoms may also be contaminated
Before caring for a patient, establish whether they were only irradiated (no hazard to you) or may also carry radioactive dust. If in doubt, remove their outer clothing and wash them first, wearing gloves and covering your own skin and breathing; see Decontamination.
What’s Next
- Learn next: Dose Thresholds — the dose bands and where sources disagree
- Combine with: Treatment Protocols — what can be done