A BOIL is an infection of the
base of a hair where it's anchored into the skin. The
germ that does this is a bacteria called Staphylococcus
aureus (pronounced: staff-ill-o-cock-us, or-I-us). The skin around
the hair becomes red, swollen, painful, and later spits out
pus.
Treatment for a boil is a course of antiobiotics - tablet
form is best as it then reaches the parts a cream can't - to kill
the Staphylococcus, pain-killers, and warm compresses
to the area.
Recurrent boils can be due to a quiet deposit of Staphylococcus
living in your nose. When transfered, eg on a finger :) to
skin they make a boil. In these persons, antibiotics are smeared
into the nostrils to kill the quiet colonies. To find out if you are
harbouring Staphylococcus fugitives in your nostrils a doctor uses
a Q-tip to stick into your nose and then sends it to the lab
where a specialist in germs tries to identify if it's growing in your
nose.
Picture of a skin boil: 
