** You must phone the laboratory for an appointment **
New Plymouth - (06) 758 7450 option 1
The test takes approximately 45 minutes.
Patients must discontinue allergy treatment and this will be discussed with the patient when the booking is made.
Antidepressants may interfere with a positive reaction (doxepin, other tricyclics, phenothiazines and tetracyclics have antihistamine activity and may need to be withheld for 1-2 weeks or more).
Other medications that interfere:
- Cold and flu remedies
- Sinus analgesics
- Sedatives
- Relaxants
- Migraine prophylactics
Skin prick testing may not be suitable for patients with widespread dermatitis or eczema, children under 5 years and patients with dermatographism (those who develop weals to all allergens as well as the negative control).
Because of increased risk and greater complexity of interpretation, skin prick testing below the age of 2 years should be considered a specialist practice (no specialist currently available in Taranaki).
Skin prick testing is not routinely indicated in the investigation of:
- Non specific rash without allergic / atopic characteristics
- Chronic urticaria in the absence of allergic features on history
- Food intolerance without allergic features (e.g. irritable bowel syndrome)
- Assessment of the effectiveness of allergen immunotherapy
- Reactions to respiratory irratants (smoke, fumes, perfumes etc)
- Food additives and occupational allergens
As skin testing carries a small risk of inducing anaphylaxis, patients who have had previous anaphylaxis or severe reactions are not suitable for this type of testing and it is recommended that specific IgE (RAST) testing be done.
Interpretation:
- A positive result does not always mean the patient will suffer an allergic illness when exposed to that allergen.
- A negative result does not entirely exclude sensitivity—these false negatives are more common in children under the age of 5.
- Food tests are the least reliable—a negative result does not exclude sensitivity.
- If all results are positive, including the negative control, the patient has dermatographism which is not due to allergy.
- If the positive control (histamine) is negative, the patient is probably taking antihistamines.
- If all tests are negative (except the positive control), the patient is unlikely to have atopic disease.
