Poison is a beverage in Survival 303.
Poison will instantly reduce your vitality to zero, causing you to die. If you are poisoned, you can survive it by eating something that heals you, such as herbs or flax flowers. Herbal remedies work the best, however.
To apply poison to a food, take the poison from your inventory out and click the food. If someone eats it, their vitality instantly drops.
The best way to poison someone is to lace the food with poison. If you give a tribe a rare food, such as the bugshark, or stew, then this will be most effective; however, many tribes may be suspicious of these gifts. The easiest way to decrease chance of suspicion is to give them a relatively common food, such as bread or salmon.
If you poison someone (or are already at war with them) you can hand them a poisoned herbal remedy to apologize.