Poison
Plenty of the delicious plants and mushrooms in the UnReal World are perfectly safe to eat snacks just waiting for a wandering adventurer to pick them up and eat them. Not all flora make for healthy snacks though, as some of them are quite poisonous. Fortunately for the culinary adventurer though, the poison can often be removed through blanching, using a pot and some water with the "Boil / Herbal beverages" cookery option. Unfortunately some plants and mushrooms are just not meant to be snacks and remain poisonous even after blanching.
The effects of poisons can be irritation in stomach and throat, hallucinations, illness, or death. The ill effects wear off after a day or two, quite permanently in the case of death.
Poisoning cannot be treated by the physician skill, but some herbal remedies may expedite the passing of poison from ones body. The best, and only, way to treat a more serious poisoning however, is to find a sage or a shaman and ask them for healing. In the case of deadly poisoning, asking a sage for healing is the only chance of survival. In such situation, it is advised to beg the sage for healing multiple times, and to be awake 8 a.m. when the game's morning check happens. Even then the odds of survival are only 1 in 3. One may try to improve these odds by praying to one's deity of choice.