Thorny Vines are a stationary hazard that damage any monsters and spelunkers that touch it. There are exceptions to this however, namely the fact that wearing Spike Boots or Spring Boots allow the spelunker to stand safely on top of the vine.
The vine will damage any monster or spelunker that touches it from any angle with a few exceptions. Wearing shoes of any kind negates damage from standing on the vine. Furthermore. some enemies do not take damage from thorny vines. These enemies include Mantraps, Mosquitos, and Skeletons.[Needs Research]
Destroying vines can help make certain situations easier. It may be beneficial to keep them around however, as certain enemies, namely Shopkeepers, are unable to get off of them, and will die from being repeatedly poked.