There are a few
tests available to indicate weather a child has specific allergies. These tests
are able to determine what substance(s) are causing an allergy.
These tests
can include:
•
Skin prick
tests
Selected
allergens are applied to the forearm or the back with a dropper, and the skin
gently pricked with a needle. A positive result shows as a red weal or flare on
the skin
within 20 minutes.
•
Allergen-specific
IgE blood tests (RAST)
These
tests are useful when skin testing is not possible or is inconclusive. A blood
sample
is taken and the level of an immunoglobulin associated with allergic
reaction (allergen
specific IgE) is measured in a laboratory.
•
Elimination
diets and challenge testing
An elimination diet is used to isolate foods that may be causing an
allergic reaction. This
usually takes a number of weeks and involves avoiding
foods identified as common causes
of food allergy. No foods or fluids may be
consumed other than those specified. If
symptoms improve, foods are added one
at a time until symptoms recur (this is known as
‘challenge testing’). Usually,
a diary is kept to record any symptoms so they can be linked
to the correct
food. This procedure must only be performed under medical supervision.
•
Patch tests
Are most commonly used to investigate
contact dermatitis. Common triggers include
fragrances (for example, in soaps).
Patches are applied to the back in adhesive strips. The
area is examined after
two and four days. A positive result shows as redness or blisters at
the site
of a particular substance.
After an
allergy test
After the
test, you can expect:
•
If you have a
skin prick test, your doctor will examine you for signs of an allergic reaction
after 20 minutes.
•
Patch tests
require further visits at two and four days after they are applied.
•
The results
of blood tests may take up to a week to be known.
•
An
elimination and challenge diet may take many weeks to provide results.
False
reactions can occur with any test, so results need to be assessed with your
clinical symptoms. Once the offending allergen or allergens are identified, you
should try to avoid or reduce exposure to them in future.
Possible
complications
Some people
with allergies experience severe reactions when exposed to particular
allergens. For example, the red weals associated with skin prick tests can be
painful, inflamed and irritated.
Some
reactions, such as anaphylaxis, is potentially life threatening. It is
important that allergy tests are performed by a qualified health professional that
can anticipate and treat any allergic reactions you may have.