What is plant toxicity?
It’s a naturally occuring, chemical process of a plant defending itself against being eaten (herbivory). Some plants create or secrete what are called secondary plant metabolites. The purpose of these of course, is to defend against herbivory. This is a mostly successful process. Plants have been doing this for millions of years. For example, poisonous sap from a rubber tree protects it from many herbivores.
Not all secondary plant metabolites repel though, and some may actually attract plant-eating creatures. Some metabolites are irritating, but not fatal. Aroids like the pothos create crystal raphides which are physical irritants, but are by no means fatal. Raw succulent juices are not fatal either, but can induce vomiting. Limonene is the compound that gives lemons their citrus scent. While fatally repellent to moths, it is pleasing to humans.
Remember, a plants’ toxicity can make us sick or worse, but only if consumed. As long and you are not chewing on your houseplants, you should be fine. We do encourage talking to, petting and even dancing with your houseplants any chance you get (although, maybe not your cactus).