Allergy Testing
Allergies commonly tested for are grass and tree pollen, fungal
spores and cat and dog. There are tests available for other
allergens.
What is an allergy?
When exposed to certain substances some people have an
exaggerated immune response. In type 1 allergy, their body produces
antibodies, which is its way of preparing to fight an attack. This
is called sensitisation. When the body is again exposed to the
allergen an allergic reaction occurs. The antibodies stick to the
allergen particles. Within minutes this initiates histamine
production, which in turn causes a number of what may be unpleasant
reactions the body. There may be rashes on the skin, swelling
inside the nose, an increased production of nasal secretions and
constriction of the respiratory passages. In severe attacks it may
become difficult to breath; the blood pressure may drop producing
dizziness or collapse.
In type 4 allergy, the reaction is delayed by hours or days and
involves white cells and not antibodies. It shows up in the area of
skin that has been in contact with the allergen, producing itchy
dermatitis.
There are a huge variety of naturally and synthetically
occurring allergens which you may be exposed to everyday. Accurate
identification of the cause of the allergic reaction is important
so that in future it can be avoided. Various tests are available to
aid identification.
Initial Consultation
Once you have been referred by your GP you will need to ring
Ashtead Outpatient Department to speak to one of our Outpatient
Specialist Nurses. She will take a detailed history regarding the
problems you have been experiencing.
Providing it is appropriate and you are not taking any
medication which may interfere with the test - you will be offered
an appointment.
The skin test is safe and causes little discomfort. It takes
about 20 minutes and you will see the result for yourself. We will
send a copy of the result to your GP. You will need to arrange a
further appointment with your GP to discuss the results.
Skin Prick Test (For Inhaled Allergens)
In this test a small amount of allergen is introduced into the
upper layer of skin, usually on the forearm. To enable small
children to be more relaxed, the back can be used.
After 20 minutes the site is examined for any sign of reaction.
If it has become red and itchy possibly with a white swelling or
weal, an allergic reaction may be indicated. The weal should fade
within a few hours.
Patch Testing (For Type 4 Allergy)
If this type of test is required your GP must refer you to a
Consultant Dermatologist.
There are many substances that can cause inflammation of the
skin. Irritant substances are those of which cause inflammation to
almost everyone, if applied at sufficient dose for long enough.
Allergens are substances which only cause a reaction to
susceptible individuals who are sensitised. Patch testing helps to
differentiate between irritants and allergens. It involves taping a
specific allergen onto the skin underneath tiny special aluminium
discs. They remain in contact with the skin for 72 hours during
which time the skin should be kept dry. The patches are removed and
30 minutes later the previously patched skin is examined for any
allergic changes.
Common allergic substances tested by patch testing include,
fragrances, lanolin dyes, preservatives, polymers used in nail
varnish, adhesives, paints and other household products and nickel,
but there are many others available. The results will be sent to
your GP and you will receive a copy.
To make an appointment or for further information please call
our Outpatient Department on: 01372 221441