The Sacrament of the Anointing of the Sick is for those who are seriously ill or in danger of death or suffering the difficulties of old age. The Sacrament may be received each time the believer falls seriously ill or an illness worsens. -- Catechism of the Catholic Church, no. 1529.
The rite of the Anointing of the Sick includes the anointing of the forehead and hands of the sick or other parts of the body accompanied by the liturgical prayer that asks for the grace of the Sacrament. -- United States Catholic Catechism for Adults, p. 257.