https://www.reddit.com/r/pics/comments/2xpflk/the_complete_story_of_the_chernobyl_accident_in/

Once exposed, nausea and vomiting will begin almost immediately, and within a short space of time your tongue and eyes will swell, followed by the rest of your body. You’ll feel weakened, as if the strength has been drained from you. If you’ve received a high dose of direct exposure - as in this scenario - your skin will blanche dark red within moments, a phenomenon often called nuclear sunburn. An hour or two after exposure, you’ll gain a pounding headache, a fever and diarrhoea, after which you’ll go into shock and pass out.

After this initial bout of symptoms, there’s often a latent period during which you’ll start to feel like you’re recovering. The nausea will recede, along with some swelling, though other symptoms will remain. This latent period varies in duration from case to case, and of course it depends on the dose, but it can last a few days. It’s cruel because it gives you hope, only to then get much, much worse. The vomiting and diarrhoea will return, along with delirium. An unstoppable, excruciating pain seethes through your body, from the skin down to your bones, and you’ll bleed from your nose, mouth and rectum. Your hair will fall out; your skin will tear easily, crack and blister, and then slowly turn black.

Your bones will rot, forever destroying your ability to create new blood cells. As you near the end, your immune system will completely collapse, your lungs, heart and other internal organs will begin to disintegrate, and you’ll cough them up. Your skin will eventually break down entirely, all but guaranteeing infection. One man from Chernobyl reported that when he stood up his skin slipped down off his leg like a sock. At high doses, radiation will change the very fabric of your DNA, turning you quite literally into a person other than the one you were before. And then you’ll die, in agony.