I rarely use followers, because I find they get in the way, trigger traps like dopes, and are often just collateral damage for the shock and awe of area-effect spells that I like to dole out.The game treats permanent (non-canine) followers in a similar way to "essential" NPCs, but still allowing the possibility of their death. When your follower would die due to an enemy attack or a trap, they will be incapacitated for some time and begin to recover their health, just like essential NPCs; enemies will stop attacking or targeting them during this time. However, if they lose all their health again during this period, they will die for good. Thus, you should try to move the fight away from them, so that they are not hit by a stray arrow or area-effect spell. They can also die if hit with a damage-over-time poison that is stronger than their health recovery. They can also die from enemy power-attacks, as well as your own "friendly fire" attacks.
If you strike your follower dead, on the other hand, there is no recovery. Attack carefully when your follower is low on health. Follower death by yourself, even accidentally, counts as murder on your crimes list.
Many temporary followers are "essential", so they cannot be killed, only incapacitated for a while. Non-essential ones will die immediately when struck down, just as ordinary NPCs.
To ensure follower healing, make sure you give them healing potions and food to carry in their inventory. This way, once a follower is "wounded" they may heal almost immediately and return to the battle. If a follower isn't carrying any healing items, you may have to wait until all enemies in the area are removed before they will heal themselves.
You can also hold down the A button and instruct a follower to interact with an object. This is particularly useful if there is a locked chest or door that you can't open yourself.



