Skin Prick Test

Allergy is the ability of animals and humans to develop altered responses to foreign substances after repeated exposure. It is a hypersensitivity reaction initiated by immunologic mechanisms.

SKIN TEST  IS ………

• Confirmatory test
• Simple
• Rapid
• Low cost
• Highly sensitive
• Reproducible

• Factors involved in allergy skin testing
• Quality of allergen extract.
• Diluting fluid.
• Preservatives.
• False positive reactions.
• Irritating reactions.
• Negative & Positive controls.

Indications of skin prick tests

• To confirm atopy, assisting in the diagnosis of asthma
• Before initiating immunotherapy
• To monitor progress during immunotherapy
• Acute Urticaria & Anaphylaxis
• Occupational Diseases including latex allergy
• Eczema
• Some drug reactions: Penicillin
• Stinging insect anaphylaxis
• Rhinitis vs Sinusitis

SPT is easy to perform and rarely causes generalized reactions.  A positive SPT indicates the presence of IgE antibodies against that allergen but does not indicate clinical sensitivity. A correlation between the history and SPT is essential.
The results can be unreliable if the patient takes certain drugs, such as anti-histamines and tricyclic anti-depressants.