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Diagnosing Food Allergies and Intolerances 189
Between 2 and 4 per cent of children 1–3 years ●● details of any previous treatment or exclusions
old are affected but most grow out of it by about and the response.
3 years of age (Zuberbier et al. 2004, Venter et al.
2008). Those with slow onset symptoms are more A paediatrician or allergy clinic can organize
likely to outgrow their food allergies than those additional investigations that may be helpful,
who experience rapid appearance of symptoms. In including:
general (Venter and Arshad 2011):
●● specific IgE testing
●● 80–90 per cent of infants will outgrow their
milk allergy by 3 years ●● skin prick tests (SPT)
●● 50 per cent of infants will outgrow their egg ●● patch tests
allergy by 3 years
●● endoscopy and biopsy.
●● 20 per cent of children may outgrow their
peanut allergy. There is no clinical or scientific evidence to support
the use of various other tests including hair
Only about 2 in 100 toddlers remain allergic to analysis, kinesiology and bioresonance (NICE
one or more foods as they get older. Children 2011). However, many alternative therapists use
should therefore be retested with a food challenge them.
at an appropriate age to check if they have grown
out of it. Specific IgE tests measure the level of
food-specific IgE levels in the blood and are highly
Diagnosing Food Allergies and predictive of foods causing allergic reactions.
Intolerances However, a child with a high food-specific IgE level
will not always have an adverse reaction to that food.
There is no simple diagnostic test for food allergy
or food intolerance. A detailed history is an A positive skin prick test causes redness and
important part of the diagnosis, and the National swelling of the skin. The size of the skin wheal
Institute for Health and Clinical Excellence (NICE) formed is graded. They are:
recommends the following points are included
(NICE 2011): ●● rarely negative in someone with true
IgE-mediated allergic reactions
●● individual and family history of atopic disease
– eczema, asthma, allergic rhinitis and also food ●● almost always negative in non-IgE-mediated
allergy – in parents or siblings reactions.
●● any personal history of atopic disease especially However, a positive blood or skin test can be seen
eczema in the absence of food allergy. The positive blood or
skin response merely means that the child is
●● the suspected allergen making IgE to the proteins in that food. There is no
need to avoid a food that a child is regularly eating
●● details of any foods that are avoided and why without symptoms even if the SPT or blood test to
that food is positive.
●● presenting symptoms and other symptoms that
may be associated with food allergy, including If the child has a history of a reaction to a food,
age of first onset, speed of onset, duration, however, and the SPT or blood test is positive, that
severity and frequency, reproducibility of would mean a clinical allergy in most cases and the
symptoms on repeated exposure and what food food needs to be avoided. A food challenge may be
and how much exposure to it causes a reaction needed for a definitive diagnosis in some cases.
●● feeding history (e.g. weaning) If the SPT or blood test is positive and the
child has never knowingly eaten the food, a
food challenge will be needed to rule out food
a l lerg y.
