If you have adventurous pets, having a spiky indoor cactus plant may lead to the odd thorn in a paw. However, this is an issue that can be easily resolved by positioning your cactus in a spot out of reach of your furry friends, or in a room they aren’t allowed to go in. Don’t worry though, almost all cactus plants are not poisonous to humans or pets, so if they do get accidentally eaten, you will see some nasty side effects, but it won’t be fatal.