Dogs instinctively don't get very close to plants that are poisonous to them. However, they may act differently than usual when they are in an agitated or stressed out state. Even if your dog doesn't have a tendency to touch plants on a regular basis, you should pay attention regularly.
Plants that are dangerous to the skin
Fig tree
Monstera
Tomato (the blue ones are poisonous).
Plants that are particularly toxic
Meadow saffron (colchicum)
Hellebore
Lily of the valley
If your dog bites into any of these plants, hurry to get him/her to an animal hospital. You should never let your dog take human medication on your own. There are some common methods like giving your dog a thick saline solution to make him/her vomit or giving your dog milk to make him/her have diarrhea. However, this should also not be carried out on the basis of personal judgment. Contact your veterinarian by phone or other means and ask for instructions.