infection involves the face and eye and
is called herpes zoster ophthalmicus.
Herpes zoster is caused by the vari-
cella–zoster virus, which also causes
chickenpox. After an attack of chicken-
pox, some of the viruses survive and lie
dormant for many years. In some peo-
ple, a decline in the efficiency of the
immune system, especially in old age or
because of disease, allows the viruses
to re-emerge and cause herpes zoster.
Herpes zoster is also common in people
whose immune system is weakened by
stress or by certain drugs, such as corti-
costeroid drugsor anticancer drugs.
The first indication of herpes zoster is
excessive sensitivity in the skin, fol-
lowed by pain. After about 5 days, the
rash appears as small, raised, red spots
that soon turn into blisters. These dry
and develop crusts that drop off, some-
times leaving small pitted scars.
The most serious feature of herpes
zoster is pain after the attack (posther-
petic pain), caused by nerve damage,
which may last for months or years.
Herpes zoster ophthalmicus may cause
a corneal ulceror uveitis.
If treatment is begun soon after the
rash appears, antiviral drugs, such as
aciclovir, will reduce the severity of the
symptoms and minimize nerve damage.
Analgesic drugsmay also be helpful.
heterosexualitySexual attraction to
members of the opposite sex. (See also
bisexuality; homosexuality.)
heterozygoteA term used to describe
a person whose cells contain 2 different
allelescontrolling a specified inherited
trait. A homozygotehas identical alleles
controlling that trait. (See also inheri-
tance; genetic disorders.)
hexachlorophaneAn antibacterial drug
used in dusting powder form to prevent
staphylococcal infections in newborns,
and to prevent and treat pressure sores.
hiatus herniaA condition in which part
of the stomachprotrudes upwards into
the chest through the opening in the dia-
phragmthat is normally occupied by the
oesophagus. The cause is unknown but
it is more common in obese people and
thosewith a long-term cough, such as
smokers. In some cases, it is present at
birth. Many people have no symptoms.In some people, there is acid reflux. This
may lead to oesophagitis orheartburn.
Antacid drugsor H 2 blockers may be
given to reduce stomach acidity. In
severe cases, surgery may be required.
Hib vaccineA vaccine administered rou-
tinely at 2, 3, and 4 months of age to
provide immunity to the bacterium HAEM-
OPHILUS INFLUENZAtype b (Hib). Before
the vaccine was generally available, Hib
infection was a common cause of bacter-
ial meningitisand epiglottitisin children.
hiccupA sudden, involuntary contraction
of the diaphragmfollowed by rapid clo-
sure of the vocal cords. Most attacks of
hiccups last only a few minutes, and are
not medically significant. Rarely, they may
be due to a condition, such as pneumonia
or pancreatitis, that causes irritation of the
diaphragm or phrenic nerves. Chlorpro-
mazine, haloperidol, or diazepammay be
prescribed for frequent, prolonged attacks.
Hickman catheter A flexible plastic
tube, also known as a skin-tunnelled
catheter, that is passed through the chest
and inserted into the subclavian vein,
which leads to the heart. It is often used
in people who have leukaemiaor other
cancers and need regular chemotherapy
and blood tests. The catheter allows
drugs to be injected directly into the
bloodstream and blood samples to be
obtained easily. The catheter is inserted,
under local anaesthesia. It can remain in
position for months; the external end is
plugged when not in use.
hidradenitis suppurativaInflammation
of the sweat glandsin the armpits and
groin due to a bacterial infection. Ab-
scesses develop beneath the skin, which
becomes reddened and painful and may
ooze pus. The condition tends to be re-
current and can eventually cause scarring
in the affected areas. Antibiotic drugsmay
help to reduce the severity of an outbreak.
high density lipoproteinOne of a
group of proteins that transport lipidsin
the blood. High levels of high density
lipoprotein can help protect against
atherosclerosis.(See also fats and oils;
low density lipoprotein.)
hipThe jointbetween the pelvisand the
upper end of the femur. The hip is a
ball-and-socket joint; the smooth, roun-
ded head of the femur fits securely intoHETEROSEXUALITY HIPH