hydrocephalus (the accumulation of fluid
in the skull). A sunken fontanelle may
be a sign of dehydration. If a fontanelle
is abnormally large, or takes a long time
to close, the cause may be a brain ab-
normality or a disorder, such as rickets,
affecting the skull bones. Early closure
of the fontanelles results in a deformity
called craniosynostosis.
Occasionally, a third fontanelle is pre-
sent between the other 2; this occurs in
Down’s syndrome.
food additivesAny substance added to
food for the purposes of preservation or
to improve its acceptability in terms of
taste, colour, or consistency.
Preservatives, such as sodium nitrate,
are added to food to control the growth
of bacteria, moulds, and yeasts. Other
additives, such as antioxidants, improve
the keeping quality of food by prevent-
ing undesirable changes (they stop
rancidity in foods containing fat, for
example). Additives that improve tex-
ture include emulsifiers, stabilizers,
thickeners, and gelling agents. Appear-
ance and taste are improved by the use
of colourings, flavourings, sweeteners,
and flavour enhancers. Artificial sweet-
eners, such as saccharin, may be used
instead of sugar, especially in products
for diabetics or slimmers.
Certain additives may produce an al-
lergic reaction in some people, and some
are thought to be a factor in behav-
ioural problems in children.
food allergyAn inappropriate or exag-
gerated reaction of the immune system
to a food. Sensitivity to cow’s milk pro-
tein is a fairly common food allergy in
young children. Other foods most com-
monly implicated in food allergy are
nuts, wheat, fish, shellfish, and eggs.
Food allergy is more common in people
who suffer from other forms of allergy
or hypersensitivity, such as asthma, al-
lergicrhinitis, and eczema.
Immediate reactions, occurring within
an hour or sometimes minutes of eating
the trigger food, include lip swelling,
tingling in the mouth or throat, vomiting,
abdominal distension, abnormally loud
bowel sounds, and diarrhoea. Some ser-
ious allergies can cause anaphylactic
shock, requiring immediate self-injectionwith adrenaline(epinephrine). The only
effective treatment for food allergy is
avoidance of the offending food. (See
also food intolerance.)
food-borne infectionAny infectious
illness caused by eating food contami-
nated with viruses, bacteria, worms, or
other organisms. There are 2 mechan-
isms by which food can become
infected. First, many animals that are
kept or caught for food may harbour
disease organisms in their tissues or
organs; and, if meat or milk from such
an animal is eaten without being thor-
oughly cooked or pasteurized, the
organisms may cause illness in their
human host. In the UK, the only com-
mon infection of this type is food
poisoning. Second, food may be con-
taminated with organisms spread from
an infected person or animal, usually by
flies moving from faeces to food.
Immunization is available against cer-
tain food-and water-borne infections
such as typhoid fever.
food fadA like or dislike of a particular
food or foods that is taken to extremes.
A food fad may lead to undue reliance
on, or avoidance of, a particular food-
stuff. Fads are common in toddlers,
adolescents, and in people who are under
stress. When a food fad becomes obses-
sive or persistent, it may indicate a
serious eating disorder. (See also ano-
rexia nervosa; bulimia.)
food intoleranceAn adverse reaction
to a food or food ingredient that occurs
each time the substance is eaten, that
is not due to a psychological cause or
to food poisoning, and that does not in-
volve the immune system.
Food intolerance is often of unknown
cause. Certain foods may be poorly tol-
erated due to impaired digestion and
absorption associated with disorders of
the pancreas or biliary system. Some
people have a genetic deficiency of a
specific enzyme, such as lactase, which
is required to digest the sugar in milk.
food poisoningA term used for any
gastrointestinal illness of sudden onset
that is suspected of being caused by
eating contaminated food. Most cases
of food poisoning are due to contam-
ination of food by bacteria or viruses.FOOD ADDITIVES FOOD POISONINGF