Ate snow and didn't die on Sakhal?

Got snow, boiled it, drank the water, got a disease. Did a bit of research and found out it was heavy metal poisoning. Spent 30 minutes running around trying to find the tablets to cure it, but after a while, the disease went away. I took multivitamin pills but I think that's it. Never puked once, is there a mechanic that I'm missing here? I thought it was guaranteed death if I ate snow. Thanks in advance.