If you only care about certain kinds of objects, you should also use ObjectReference.AddInventoryEventFilter(...) to filter out any events for things you aren't interested in.

• Refer to the notes for ObjectReference.OnItemAdded(...) to get an idea of how important this is.

• If something calls ObjectReference.RemoveAllItems(...) and you don't use an inventory event filter, then for every type of item removed from the object's inventory, one call to your OnItemRemoved event handler will be queued. If the player is holding a wide variety of items, then Skyrim will queue up more calls than it can even keep track of, causing an instant stack dump. This may negatively impact your own script as well as other scripts written by other people.

  • The "Diplomatic Immunity" quest is a good testcase for this; getting thrown in jail may also work.
  • You can detect RemoveAllItems calls by making sure that the player always has a weightless non-playable item on their person, and using an inventory event filter to listen for that item's removal. Under that circumstance, only a removal of all items will ever cause your OnItemRemoved handler to fire.

If the item is consumed by any means (crafting, charging, poisoning, eat/drink) the dest parameter is None and most likely, but not always, the reference is None too.

If player uses a poison to apply it to a weapon the event is fired twice: before and after the confirmation dialogue. If canceled in the confirmation dialogue then is not fired twice.

If you need to temporarily stop OnItemAdded and OnItemRemoved calls from being queued, you can use AddInventoryEventFilter with an empty FormList as an argument. To resume listening for item additions and removals, you can call ObjectReference.RemoveAllInventoryEventFilters().

• This trick stops OnItemRemoved calls from being queued. It doesn't prevent the execution of function calls that have already been queued. To wit, using this trick from inside of OnItemRemoved won't stop Skyrim from dumping stacks when something calls RemoveAllItems(), because the first OnItemRemoved call only executes after the other hundred or so have been queued. You'd have to stop listening to inventory events before the item removals ever take place.

Remember that you can point multiple reference aliases at the player. Each can have their own inventory event filters and inventory event handlers, so you can filter OnItemAdded and OnItemRemoved differently.