He Anoints my Head with Oil

Psalm 23: "The LORD is my shepherd; I shall not want.
He maketh me to lie down in green pastures: he leadeth me beside the still waters. He restoreth my soul: he leadeth me in the paths of righteousness for his name's sake. Yea, though I walk through the valley of the shadow of death, I will fear no evil: for thou art with me; thy rod and thy staff they comfort me. Thou preparest a table before me in the presence of mine enemies: ​

Thou anointest my head with oil 

​my cup runneth over. Surely goodness and mercy shall follow me all the days of my life:
​and I will dwell in the house of the LORD for ever."

Sheep are especially troubled by the nose fly. These little flies buzz around the sheep's head, attempting to deposit their eggs on the damp, mucous membranes of the sheep's nose. If they are successful, the eggs will hatch in a few days to form small, worm-like larvae. They will then borrow and work their way up the nasal passages into the sheep's head which will create intense irritation accompanied by severe inflammation.
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For relief from this agonizing experience, sheep will deliberately beat their heads against trees, rocks, posts, or brush. In extreme cases of intense infestation, a sheep may even kill itself, because death is better than this agony.
To prevent this, the good shepherd will apply an oil antidote to their heads. The Hebrew text ḇaš-še-men, gives us some insight to this concoction. It comes from the root word, shamen, which translates: choice (1), fatness (2), fertile (2), lavish (1), oil (176), oils (3), ointment (1), olive (6), wild* (1). Most likely it was a choice (used for eating) wild olive oil, infused with other oils indigenous to that area, most probably Balsam oil.

Balsam oil was highly valued in the ancient world. A jar of it was found in a cave (where shepherds might find shelter) near the Dead Sea in 1989. This oil is commonly mentioned in the Bible and also known as the "Balm of Gilead". It is soothing, anti-inflammatory, antibacterial, anti fungal, and anti-parasitic. Generally its topical use is recommended for skin rashes, eczema, and skin parasites such as scabies, ringworm, and head lice, which makes it a perfect addition to the fatty shamen oil poured on the head of the sheep.

What an incredible transformation this would make. Once the oil had been applied to the sheep's head, there was an immediate change in behavior. The sheep would start to feed quietly again, then soon lie down in peaceful contentment.
There was certainly a practical reason to anoint the head of sheep with oil, but we can also see a spiritual reflection here. The Bible commonly refers to believers as sheep. "Thou anointest my head with oil" represents His protection from the "flies" that would come to destroy us. What better way to trust Him than to nestle up closely under the protection of the Good Shepard and enjoy the safety of His anointing.

(c) Leaves for Medicine, Rachel Lee Carter