A special sacrament for the sick & suffering
The Catechism of the Catholic Church's section on the Anointing of the Sick defines the purpose of the sacrament as "the conferral of a special grace on the Christian experiencing the difficulties inherent in the condition of grave illness or old age." (Catechism, 1527)
In his Gospel St. Mark (6:12-13) gives us an indication of this sacrament of the sick when he tells us that the apostles, going forth, "preached that men should repent, and they cast out many devils, and anointed with oil many sick people, and healed them."
The Oil of the Sick
The oil used in administering the sacrament of Anointing of the Sick is called Oil of the Sick. It is one of the three Holy oils blessed by the bishop of the diocese at his cathedral on Holy Thursday morning, the other two Holy Oils being Holy Chrism and the Oil of Catechumens, which is used in Baptism.
Oil of the Sick is pure olive oil - nothing being added except the blessing of the bishop. Its appropriateness as part of the outward sign of Anointing of the Sick is evident from the healing and strengthening effects which are characteristic of olive oil.
The essence of the sacrament lies in the actual anointing and the short prayer which accompanies the anointing.
In giving the sacrament, the priest anoints the sick person on the forehead and hands. During this anointing, the priest says: "Through this holy anointing may the Lord in his love and mercy help you with the grace of the Holy Spirit. May the Lord who frees you from sin save you and raise you up."