1. Nausea And Vomiting
The earliest symptoms of Acute Radiation Syndrome (ARS) are nausea and disorientation. If you start vomiting within an hour of exposure this implies a massive dose of radiation, making it far likelier you will die without medical treatment.
2. Bruising And Inability To Heal Wounds
Radiation depletes clot-forming platelets in the blood, leading to severe bruising and wounds that won't heal. In certain cases, this manifests as purpura, discolored patches caused by bleeding beneath the skin (pictured above).
3. Bleeding Out Of Orifices
Also due to the body's inability to clot, you may bleed spontaneously from the nose, mouth and rectum.
4. Bloody Diarrhea And Vomit
Similar symptoms as above, different cause. Radiation depletes the cells of the intestinal wall and stomach. This irritates the stomach and intestines, leading to bloody vomit and stool.
5. Radiation Burns
Clinically known as cutaneous radiation syndrome, or CRS, the first sign is itching. Exposed skin may then turn red, blister, develop open sores and slough off.
6. Hair Loss
Radiation damages hair follicles, which could lead to rapid hair loss.
7. Headaches, Weakness And Fatigue
Due to anemia from the loss of blood cells, weakness and fainting may occur. Also leads to hypotension, or extremely low blood pressure.
8. Mouth Sores
Ulcers in and around the mouth, a visible manifestation of ulcers all along the esophagus and digestive tract.
9. Seizures And Tremors
Intense and prolonged exposure to radiation can impair the central nervous system. This can lead to a general lack of muscle coordination and seizures.
10. Fever And Infections
What will ultimately kill someone suffering from radiation sickness. Radiation destroys bone marrow and white blood cells, leading to increased risk of bacterial, viral and fungal infections.