Skin prick testing or SPT demonstrates an allergic response to a specific allergen.In conjunction with an allergy focused history, SPT can help to confirm the presence of an allergy to either a food or inhaled substance (allergen). SPT is a simple, safe and quick test, providing results within 15-20 minutes.This will enable you to receive a diagnosis and management plan at your appointment. The skin prick test introduces a tiny amount of allergen into the skin, eliciting a small, localised allergic response, in the form of a wheal (bump) and flare (redness) at the site of testing.
SPT is usually carried out on the inner forearm, but in some circumstances may be carried out on another part of the body, such as back or thigh.For example, there is a larger area on the back or thigh to perform testing on a baby, similarly, for those with troublesome eczema the test can be performed on any clear patch of skin. The test allergens are selected following a discussion with your clinician and based on your history ~ As few as 3 or 4 or up to about 25 allergens can be tested ~ The skin is coded with a marker pen to identify the allergens to be tested a drop of the allergen (extract) solution is placed on the skin is then pricked through the drop using the tip of a lancet – this can feel a little sharp but should not be painful and should not bleed.
The patient needs to avoid taking anti-histamines and certain other medications before the test.Long acting antihistamines (those that do not cause drowsiness) should be stopped for five days, short acting antihistamines can be stopped 48 hours beforehand.Many cough mixtures contain an antihistamine, therefore please tell the healthcare professional who is performing the test any medication you have taken.The results will not be reliable if anti-histamines are still in the body when the test is performed as antihistamines can prevent the body from reacting to the SPT. If the patient has not stopped taking anti-histamines before their appointment they may not be able to have the skin prick test.