These arrowhead shaped pieces of flint were used as weapons against animals and people. They were believed to be fatal to cattle. To save a cow that had been shot with an elf-arrow they had to be touched by the arrow, the arrow then needed to be dipped into water and the cow needed to drink the water afterwards.
Sick animals are still said to be elf-shot if they become ill.
If the person were shot with an elf-arrow, they get sick with a mysterious supernatural illness.
In 1560, a Scottish woman was accused of using of elf-arrows. Catherine Ross, Lady Fowllis, along with her son-in-law Hector Munro, and other nameless witches wanted to kill Ross’ husband and Marjorie Campbell, Lady Balnagown. Lady Fowllis wanted to marry Lord Balnagown. The plot was uncovered before anything happened to the victims. Elf-Arrows superstition is strong in Ireland, England, and parts of Scotland.
Image from Google Search.
Mari Wells 
Elf Arrows are, in fact, prehistoric Flint arrowheads that were found by our superstitious ancestors 😃
Yes, but they were also much more. Some of these Elf Arrows were dipped in poisons… Poisonous Flint 😉